I have a fanfic to work on BUT
I like the idea of Saiki having a little sister because he’s surprisingly good with kids? And, plus, he deserves some good sibling bonding that isn’t from Kusuke.
(Fun fact: My laptop died when I was writing this so this is my second go at this, ha ha)
He’s not even surprised when his mother tells him she’s preggo because he already knew from the beginning. Poor kid had to move to Malaysia momentarily to sleep that night.
And the whole family, including Kusuke, is sorta anxious the new kid will turn out even more powerful than Kusuo or at least have some sort of power/superhuman intelligence.
She’s born during Kusuo’s first year of highschool and before the volcano fiasco, so Kusuo hasn’t met any of his friends yet.
After several months of nothing, they finally conclude Saiki Kuriko does not have psychic powers or super intelligence.
This fascinates Kusuo sorta, because she’s a small child. A small defenseless and fragile child, and it worries him a little because she doesn’t have powers, so she can easily get hurt.
So his parents just casually watches him sit five feet away from the crib and every so often he would cross his eyes to use clairvoyance to make sure there’s no incoming danger and look over at her crib to make sure she’s okay and breathing.
He won’t admit he’s being too paranoid, because that’ll make him look dumb, so he’s always trying his best to look normal as he walks over to her crib and places a hand on her chest to make sure her heart is beating.
His second year of highschool rolls in and she’s starting get that baby fat look and she can sit up, crawl, and make weird noises now.
This only makes Kusuo panic even more because now she can crawl into danger herself.
“No, Kuu-chan, you can’t take parental leave. Besides, she’s too old for that.”
Sometimes, he’d teleport home from school just to check up on her and she’ll be on the floor playing while his mom is in the kitchen.
She looks up and makes un-contained excitement noises.
“Oh good, you’re alive.” He touches her, just to make sure. “Okay see you around.” And he disappears.
And it’s not the first time she has seen him done that, but it still spooks her into momentary silence.
“Riko-kun, did your brother just teleport into the house again?”
She can’t answer of course, but her mother is trying.
After the first earth reset to prevent the whole of Japan from ending in disaster, he’s a little bummed out when he realizes he won’t be seeing Kuriko grow older any time soon.
Kusuke meets little Kuriko for the first time during the time Kusuo’s limiter broke, and the first thing he does is leave her in a crib while he plays tag with Kusuo. Kusuo makes sure to give her all his strawberries from his reward cakes as an apology for leaving her with that vile creature.
Visiting grandparents is a lot different now because now his grandfather is more interested in tiny Kuriko than Kusuo. And as much as Kusuo enjoys the fact that his granddad isn’t harassing him anymore, he’s kinda uncomfortable leaving her with him. Granddad still adores him, he just likes the baby more.
And honestly, she’s a baby, so who wouldn’t?
Anyways, cue Kusuo’s friends meeting tiny baby: