The old thing I saw was for a different AU that I've abandoned. I got bored and decided to adapt it to LostTale, the AU where I showed the timeline of. I wanted to do ConqeurorTale but it just didn't fit. LostTale made more sense. So... without further ado. Here it is.
Flowey rummaged through Sans's drawer which was filled with scientific papers. Nothing interesting, Flowey thought. As he rummaged something caught his eye. An envelope. Odd, who would Sans be writing letters to? "Hey, Trashbag, what's this?" Flowey asked.
Sans was laying down on his bed not paying attention to Flowey. "no clue. read it if you want."
Flowey hissed. Seeing that he's not gonna get answers from Sans, he opens the envelope. Inside was a letter addressed to him, odd. The letter read,
"
Dear Asriel,
I’m sorry those are your parents, let me be honest. It takes a lot to make me hate, but your parents made me acknowledge. That seeing them made me wish they died in that war we fought in. I'm sorry that you gotta grow up where you're forced to stand behind them. Life is hard, I know, big mistakes are nothing new to your folks. And those mistakes go down to you that’ll stick to you as you grow. You were a good kid that needed good leadership. If I was your mentor, you wouldn’t have died on those surface plains.
Never pretend to be something you’re not, bud. Either you stand right back or fight with your whole chest, bud. Never fall and lose authenticity, that's bad religion. Please remember, you could be a bitch even if you got riches.
Never fence sit, if you believe it’s wrong, know to push back. Even with all of them pressuring, don’t back down, get some integrity. Don't cut the crown like mommy did, fuck what the queen did. Mommy fled away to disengage, don’t copy cowardship.
Understand, no waging war with shaky hearts, that's law. Feed to rage and you’ll lose it all, that's how we’ll end as dust. Your daddy traded integrity. That’ll doom us all. Few of us survived that war, we don’t want one more.
Be proud of who you are, your strength comes from within. Many monsters to admire, but your parents aren’t one of them. Don’t let emotions rule like them, you'll carry yourself a true king.
I know this letter is late. Know your death is caused by them.
Sincerely,
Sans
"
Flowey winced at what he read but at the same time he couldn't help but find it amusing. "Gotta hand it to you, Trashbag. You weren't kidding when you said you hated my parents."
"What?" Sans eyes went dark. "Gimme that." Sans snatched the letter from Flowey's vines. His perplexed expression turning into one of shame upon seeing the first line. "...I thought I burned this."
"Why? Couldn't handle the shame?" Flowey smirked.
Sans looked to the side. "It was so uh... you can see it in the afterlife."
Silence falls between the two.
"You really are something, aren'tcha, Sans?" Flowey said. "Let's show it to that turtle."
"Don't"
Some context on why Sans vehemently hated Asgore and Toriel here. In the timeline I showed, Sans grew up in war and was a conscript of war. He saw the Monster Kingdom at its peak in the surface and subsequent fall nearing extinction. The Sans in this AU would be absolutely against Asgore waging war against humans. Especially since when Chara fell, it was only decades after they lost. They were nowhere near close to their peak and was in the early stage of rebuilding their lost glory.
One final thing, if the letter sounded familiar that's because it is heavily inspired by the first verse of Meet the Grahams by Kendrick Lamar. That's the time I learned that I wasn't hating to my full potential.