Hcs bout a post tybw arc living world mission - somethings wrong with a high school, so toshiro gets sent to infiltrate and investigate and kensei gets forced to play dad. (Kensei getting hit on by the single dad of the girl whos hitting on toshiro entirely optional...... *twiddles thumbs*)
So Toshiro looks like a grade schooler. This is a fact.
But since he talks like an adult and also has physical skills beyond a grade-schooler even for what he’d show in the human world (say, better hand-eye coordination), it’d be easier to pass him off as a kid in junior high who’s just really tiny. Junior High in Japan is grades 7-9, or about 12-15 years old.
So Toshiro’s cover story is that he’s a shrimpy 13-year-old, probably who had some sort of medical condition as a little kid, but he’s fully recovered and now in public school. This explains a lot of the physical oddities like his size and hair color, and a lot of his social oddities since he’d be in the hospital a lot and/or homeschooled instead of in the public system.
Kensei is the Hot Single Dad. He’s played off as a writer, so he can have a reason why his schedule is so flexible
Toshiro has a decent amount of trouble fitting in at school - he’s not used to what’s expected of him. Luckily they thought of the homeschooling thing, which gets him a few free passes since it explains why he just doesn’t know what’s normal in the school system - say, procedures for cleaning the classroom, or how to greet the teacher, or even the bell schedule
Kensei and the other Visored help a lot, but they are of limited help for stuff that’s specific to junior high schools, since those of them that could even fake being a student couldn’t pretend to be that young
they’re there for some sort of illicit goods trafficking (not Urahara, but someone else who’s not as smart and didn’t help save the Soul Society from certain destruction)
Toshiro ends up kicking ass and taking names
and at least three of his classmates think he’s hot stuff
Toshiro is 100% freaked out by being approached for friendship by kids
because when he was an actual kid no one wanted to be his friends and now these human kids think he’s cool???