Well, I've got Toushirou's family pretty comfortably established: no siblings, dead parents, mom was an only child, dad's family is back in Japan. Granny is basically what he's got, and I'd kind of prefer she remain NPC.

Toushirou isn't the most social, but as far as acquaintances? He's on his school soccer team, so there may be other members of that, as well as coaches or other support staff. He's a noticeably gifted student, so if there are any potential middle-school teachers out there, they might recognize him and vice-versa. Also, he's small for his age and kinda bratty, so he's had some issues with bullies, if anyone's got a more mean-spirited youngster out there.