The Beginning of that draft fic I've been playing with, which is up to 5 parts in my WIP folder so far.
'Senku built a time machine' story with a twist
Edit 12-Mar-2026: Now on AO3 as Point Your Kaleidoscope at the Sky
Senku had worked hard and made so many sacrifices. He dedicated his life to preventing the destruction of human civilization. He collected all the components, pushed scientific understanding to the edge, kept at it even after he was old and gray, and finally managed to make something that might qualify as a time machine. He’d done his very best, but the results of every test came back the same.
You can’t break causality. You can’t send matter.
The only way to go back in time and get a do-over was to break into the multiverse. It was suicide, twice. Once for who you were, and once for the you that you replace. Except of course that a branching timeline would carry the you that you replace along as if it never happened to become the you that dies when you go back, but the you that left your original timeline would die in every way that mattered. Total brain death, and every shred of chemical energy in the body burnt to ash. It was only by glancing through windows in timespace into other realities that he knew that it worked on his test subjects, and admittedly interpreting the behavior of animals was hard. The ravens he’d taught to speak very specific phrases certainly seemed to carry that knowledge into alternate timelines.
The project had trudged along for decades. Xeno called it their theoretical hobby, when he was still alive. Xeno and Stanley died a few years ago, one to lung cancer and the other in his sleep in a way nobody could prove was self-inflicted poison. Senku had been working mostly on this by himself in his free time for a while.
Gen came charging into the lab shortly after Senku finished compiling his findings. He wasn’t sure how Gen found out about the final results, perhaps one of Senku’s students had sent an email. Gen had long hair now, all a bright white bound in a leather thong that would be very masculine if it didn’t have flowers embossed on it, and leaned hard on a cane. He was full of demands. ‘Don’t you dare’ and ‘Stop this madness’ and ‘Burn it all’ and even ‘Take me with you.’
“Senku, please, you had a stroke last month, you aren’t well,” Gen insisted. “I know, I really do, that it seems like a solution to you, but to me it sounds like it can’t work. You can’t go back and prevent all this.”
“I can make a new timeline, where it doesn’t happen,” Senku insisted.
“By destroying yourself,” Gen said, slowly and with great emphasis.
“An entire world that is better off.”
“A world without you.”
“I’d be there.”
“Young you would die. Your brain patterns would overwrite him. This old soul you have in here,” Gen pressed his hand to Senku’s chest, “deserves rest, deserves peace, not to go through all that again. Let things move on, let this new generation progress, don’t erase what we’ve done. So much of it is good, even with how much is gone forever.”
“This world will go on,” Senku insisted. The rest of their talk boiled down to Gen not wanting to bury Senku’s fried remains.
The last set of demands sounded a lot like Xeno saying he didn’t want to see another sunrise after Stanley’s death, when it was clear the cancer treatment wasn’t working anymore and the old soldier was wasting away.
Gen and Kohaku had a nice life, Senku thought. She’d tried it on with Senku after the moon mission finished, and for Senku the sex was bad and the rest was just the same friendship so he didn’t see the point. Then Gen was there to let her cry on his shoulder. Maybe he misjudged that, missed a few variables. Kohaku was still around, a grandmother and one of the heros who fixed the world spending her time telling stories. Gen was a great father by all accounts, but they were busy people and traveled a lot. That they didn’t travel together hadn’t registered as odd, but then he had thought Gen was gay right up until the moment the two of them announced their engagement. He’d thought he’d just gotten that wrong, since he seemed to be missing some of the instincts that let normal people handle romance entirely. Maybe Gen and Kohaku bonded over something messier and sadder than love for each other. It had hurt, when Gen married Kohaku, and he hadn’t wanted to waste time figuring out why when they seemed so happy, but it had hurt him in a way that never really stopped hurting.
He figured maybe he’d give Gen this one last thing, since it mattered so much to him, and Senku had always wanted Gen around even when it hurt.
--------------
The first thing he thought, when he woke up the next morning, was that something had gone very wrong. The second was that he didn’t have any long-term experiment running that could have gone wrong. He’d had the strangest dream of being an old man in a wheelchair arguing with another old person who was at once too pretty to be a man and too sharp-angled to be a woman. They were familiar, and looked at him with a longing he couldn’t quite place.
All day he had the strangest feeling of deja vu. He felt like he already knew the information in all the books on his reading list. Like he read them a long time ago, and was just refreshing his memory, which was a bit of a novel thing for his brain to self-report given his near-perfect recall. The only thing he could compare it to was looking at his old toys that Byakuya took out of storage to donate last spring. Something so old that the information had worn away on the edges, but was still distantly there.
The school day was a lot of self-study for him broken up by phys ed, domestic arts (he wasn’t a girl, but the school had him attend extra electives since he was so far ahead in his core classes, and he didn’t mind because the girl he’d been assigned to sit next to thought it was awesome that NASA’s Apollo mission computers had woven core memory made by hand by women,) music class, and the technical class the remedial students had to take. Senku didn’t know why a class all about using tools, making things, and precise technical drawing was reserved for only the worst students, he thought it was a lot of fun learning the names and uses for different kinds of wrenches and the practical physics of load bearing walls. It was also full of demonstrations and lessons that would be hard to learn from a book even for someone like him.
As had become usual, some guys who didn’t understand he was taking an all-girls class because he would be bored to the point of doing a dangerous and distracting experiment if they forced him to sit though the regular science and math classes tried to make something of him being in their masculine applied technology class when school let out. His brain kicked up thoughts of androgynous people, like the old man in his dream and someone of French ancestry who refused to be labeled. It was confusing and their bullying felt more personal and hurtful than usual in a way that made him uneasy and scared, even though it was just the usual bullshit.
When he got home, he had an email from Dr. X that also seemed oddly familiar. He also… but that wasn’t possible. He couldn’t know that. Why would he know that? They only talked about science. The only way to prove anything conclusively was to test it, so Senku did.
Dr. X, can I ask off topic a question? You can just ignore my next mail if you don’t want answer.
Senku.
He clicked send on the shortest message he’d ever sent to his mentor. It was also the least formal, he hadn’t included a salutation and signed with only his given name. Was that rude? He’d written it completely in English, too. Was his English correct? He’d been practicing a lot lately, but he’d typed it rather fast, and he hadn’t checked any of the words before sending it. It was wildly out of character, he usually took his time when writing to Dr. X to make sure the message was as precise as possible. Well, too late. Dr. Xeno responded almost immediately, most of his answer appearing in both Japanese and English in separate sections.
Dear Senku,
While our relationship as teacher and student has been limited generally to rocket propulsion systems and material science thus far, I would hope you consider me a trusted adult available if you require assistance or advice. You can ask any serious questions, and I will do my best to give an appropriate response.
Sincerely,
Dr. Xeno Wingfield, MNAE
Only in Japanese he added: “Your English is quite good. You have clearly been practicing often. I look forward to more bilingual communication as you improve.”
Additionally, and only in English, Xeno wrote: “Language barriers are an imperfect means of secret communication, but can be effective enough. Are you safe? I will answer the next message in the language you choose.” Senku wrote back as fast as he could form the words in English, without even including a signature line.
I’ll never want marry a girl. They make good friends. Do you like boys?
Senku had just about worked himself into a full panic when Dr. X responded an hour later.
The first third of the email was about the difference between an adult man liking boys and an adult man liking men. He listed the phone numbers Senku could use to contact his local police and social services and also a link to an anonymous support website for sexual abuse victims. Senku probably should have specified that he was safe, but he honestly hadn’t understood why Dr. X had included the question in the first place until reading all of that.
The rest of the email was resources for LGBTQ people. It was honestly impressive that Dr. X had compiled such a long list of resources so quickly, but he was a professional researcher and he did qualify that he had only vetted the first group of links, and got the second longer set through a Japanese parenting website that seemed friendly, but Senku should proceed with caution when browsing them. Dr. X firmly believed that any claim of ‘curing’ queerness was complete nonsense he should ignore as bigotry and pseudoscience. He highly recommended the English language comic website Oh Joy Sex Toy for the accuracy and frankness of the educational section and hoped Senku would be mature about the product review section, provided Senku was fluent enough to read any of them and mature enough to have genuine interest in how such things were used.
Attached to the email was an image. He’d only ever seen the official headshot of Dr. X on the NASA website, but in this picture, he was dressed casually in what Senku thought was a band t-shirt with “Voltair” written in big letters under a guy dressed like a vampire, a black buckled collar choker, and a short leather jacket. He was at an airport leaning against some kind of railing or barrier, and an airplane was taking off in the large window behind him. He looked happy and relaxed, which shouldn’t shock Senku so much since he never talked about any personal stuff before now to have an opinion on how happy Dr. X was on an average day, but even more shocking was the man in the picture with him wearing what a quick internet search confirmed was a US Marine uniform. Also, the man was kissing Dr. X on the cheek, but on the list of surprising things that one was understandably at the bottom after the supportive and protective email he’d just read.
Senku knew that face. He shouldn’t, but he did. He couldn’t remember why he knew that face, but seeing a man with the name SNYDER embroidered on his uniform pocket kiss Dr. X made sense in a way it shouldn’t. He thought Snyder’s hair was wrong, which was a very dumb thing for his brain to think of someone he’d never seen before. Soldiers had to cut their hair really short. When he wrote his answer, he used a couple Japanese words if he wasn’t sure about a word, but decided to try and write as much as he could in English and do a better job of communicating.
Dear Dr. X,
Thank you. Mr. Snyder looks nice and you look happy.
I am completely safe from everything you are worrying about in the beginning, but will save this message for future reference in case I ever need any of that, even just to share with someone else. I’m sorry for any worry I might did[?] un-it-tentional [spelling!] caused. I should explain: I panicked when I wrote to you. Today has been weird/bad.
My best friend likes the girl I sit next to in domestic class. Is that what it is called in America? I just translated the class name but the definition of domestic seems not right when I reverse the translation. The class with home safety, cooking, budgeting, and sewing that only girls take. And me because the school manager [? gakkō kanri] insisted. I just imagine I’m sewing a space suit or woven memory computer together when we’re doing sewings in class and she likes hearing about NASA history. We don’t want to kiss. Not me and Yuzuriha or me and Taiju. Not me and anyone. I am only twelve years now, so maybe later? Taiju is my best friend. You’ve seen him in some of pictures I sent you of my rockets because he helps me with them. I don’t have a good picture of Yuzuriha. I did invite her to the next rocket launch.
There are some boys at school who don’t understand why I take classes that are only for girls if I wear a boy’s uniform and my student ID says boy. I don’t let it bother me, most times, but it was different today. It’s just because I’m so far ahead I’d be bored in most of the regular classes, same as for the class for remedial students that’s all about making things out of wood and what all the tools do. We’re not allowed to use any of the power tools. I wish. We are making bridges and strongest wins. Everyone wants me on their team except for ones calling me a girl for sewing.
So they will lose.
Your Student,
Ishigami Senku
Senku triple-checked he didn’t say anything that might make Dr. X worry more and sent the email. He tried to just move on, to let himself be distracted by browsing all the stuff about LGBTQ youth and gay pride in America and Japan his mentor sent him, but the odd feeling of knowing things he shouldn’t kept coming back. He responded properly to Dr. Xeno’s original email about his latest rocket model and the launch preparations separately.
A week later Byakuya took Senku out for a very early dinner of their favorite ramen and then way out to the national park. It was a long train ride, and they talked about school and one of Byakuya’s coworkers’ upcoming marriage. A trip to look at nature wasn’t completely abnormal, but there was usually some planning or something special going on. With it being a school night with no holidays or special events this week, it was mostly tourists and vacationers in the park. Byakuya found a nice place to sit down that was a bit out of the way, took a deep breath, and interrupted Senku’s increasingly nervous chatter.
“You know the computer has a nanny program on it,” Byakuya said. “I did disable the feature that completely prevented you from seeing anything with the default list of key words, though there are still a few specific websites that are blocked. What you might not know is it sends me an email with a summary of what you have been looking at if you do go to places the default list would have blocked.”
“Shit,” Senku said, looking down at the ground.
“That’s… a fair enough reaction. Anything you want to talk about?” Byakuya asked.
“I’m not sure yet,” Senku said. It was weird. There was so much stuff he just suddenly knew about, but not this. The sexual stuff didn’t have the odd ‘I’m reading this for the second time’ feeling the way that a lot of the books he’d been reading lately did. There was something he did know, from a very confusing dream about a girl who became a woman he got naked with, then became an old woman. “I don’t think I like girls as much as other boys do.”
“You are still young, but if you are wondering about it enough to research it then it’s time for a talk about it,” Byakuya said.
“We had that talk, and I know about the babies and the diseases,” Senku said.
“Well, now we get to talk about dating, preferences, and love.”
“Byakuya, the only way you are getting married is if you were one of the last men left on the planet,” Senku said confidently, a little too sure of what he was saying and unsure how he felt about the possibilities. “I’m not sure your advice would help prevent me dying single.”
“You don’t have to be so brutal about it,” Byakuya said, covering his face with his hands. “I realize I’m not exactly bringing women around all the time, and I am single right now, but I have dated since I adopted you.”
“We both know that was a disaster, the details of which I agreed to never speak of,” Senku said.
“Senku, this is supposed to be a conversation about consent,” Byakuya said, suddenly stone serious. “Also, experimentation, but mostly how to ask for things and how to say no.”
“Is it somehow not the same as trying new food, asking for what I like to eat, and saying no to food I hate?” Senku asked, parroting one of the videos he’d seen on Dr.X’s vetted resource websites.
“Yes and no. It can be a lot harder to ask for what you want and be sure the other person understands exactly what you meant without also ruining the mood, or sounding too aggressive, or being a jerk,” Byakuya said thoughtfully, leaning back to look up at the tree canopy. “I know you wouldn’t want to hurt someone, especially someone you like, but saying no to someone you like is a lot harder than saying no to a free sample of curry mushroom ice cream in a shop.”
“A crime against all dairy products.”
“Agreed, but this is something that takes practice. More than usual, first because having an incredible memory and being able to speed read won’t help you as much as it usually does with learning something new, and second because being on the autistic spectrum means you start a bit behind the curve,” Byakuya said gently. “Honestly, I thought I’d have a few more years before this conversation, I was really expecting you to be a late bloomer, but I know plenty of guys that started noticing cute girls much younger than you, so don’t think you’ve started too early. This is something it’s better to start studying up on a little before you want to use it.”
“Right.” Senku wasn’t really noticing anyone, it had been a test to see if his weird intuition about Dr. X being queer was accurate that got out of hand, but he didn’t want to just say that. He didn’t know what was going on with him and it sounded insane. Also, this felt new, and he liked that newness.
“Good. There is no getting out of it, and this is important enough I have some hypothetical situations prepared for you. I can’t assume you’ll ask the right questions without them. When you are ready for it, I’ll get you access to some age-appropriate fiction stories. Digital copies, so no worries about someone seeing the book cover and saying something about it. I found a good free digital library with clear indications of how, uh, how detailed the stories get, and I trust you to stick to a level that is comfortable for you with occasional peaks into the next level to see if you can handle more or not. Fiction stories are like thought experiments, and I think if you approach it as trying to find a type of story that matches what you are experiencing or wanting it will work better than a bunch of random web searching. Most of it will be about girls and boys instead of… any of the alternatives, but it’s a start and those stories can still show you something about first steps, fights, and how to work out problems.”
“I didn’t know what some of the words meant so I looked up a lot of definitions that have nothing to do with me,” Senku hedged. “Then there was just a lot of new information.”
“Plenty of time to figure it out. For now, let’s start with the basics.” Byakuya was gentle about it, keeping things vague for now and talking mostly about what to do if Senku saw someone he wanted to get closer to. How to say ‘hello, sexy person’ without sounding like a creep, which Senku had to admit Byakuya did know how to do. He just couldn’t keep a girlfriend. They took a break when a group of tourists passed by the patch of dirt under the trees Byakuya picked for this heart to heart, then start back up. It gave Senku a chance to process what Byakuya was saying. They ended up being out rather late, but it was a productive use of time.
Part two is in the reblogs
Part 3 in this post
Part 4 over here
Part 5 here
