Au where yata is the heir to the yakuza?
So maybe Yata’s bio dad was the head of a yakuza gang, Yata’s mom didn’t know when she married him and he tried to keep her from finding out because it would put both her and the child in danger. Then maybe someone from a rival gang finds out that Yata’s dad is married and he has to leave his wife and child behind in order to save their lives. Yata’s mom though thinks he just walked out and so she doesn’t keep many pictures of him around the house or anything and she always tells Yata that his dad was just a deadbeat who didn’t realize what a wonderful child he had. Yata grows up being loved by his mom and by his stepdad, though like in canon he always feels a little left out and like he’s the only one in the house who doesn’t quite belong. What he doesn’t know is that his dad is still secretly keeping an eye on him and his mom just in case, like living across the street from Yata is this cool guy named Mikoto and his best friends Kusanagi and Totsuka and Yata talks with them all the time and they’re actually related to the yakuza gang that Yata’s dad is head of. Their families were part of the yakuza and though the three of them rarely deal with anything from that world themselves (though Kusanagi has some occasional shady dealings going on and Mikoto’s known for being a good enforcer in the right circumstances) they agreed to watch over the boss’s family since it seemed like an easy enough assignment, they didn’t quite expect to get attached to the tiny angry ball of sunshine that is Yata Misaki.
Then when Yata’s in middle school he meets Fushimi and they become friends, Fushimi’s wary about actually becoming close with someone though because his parents are also involved with the yakuza (imagine Niki’s like a hitman and Kisa does a lot of vaguely illegal weapons exporting) and Fushimi thinks that anyone who gets close to him is likely to end up dead. Yata manages to break into Fushimi’s little world despite that and the two of them become friends. Fushimi convinces Yata to move out of his house and share an apartment with him, Fushimi thinking that this way he can hide Yata from Niki. Except what happens is this ends up inadvertently alerting some of the other yakuza gangs to Yata’s presence, like the place they get their apartment from has yakuza ties and someone spots Yata at some point and recognizes him as the person who was rumored to be the son of a recently-deceased yakuza head. The informant then leaks the information to one of the strongest yakuza gangs in the area, jungle, and boss Hisui Nagare decides that they should attack the apartment and kidnap Yata so that they can use him as leverage against the other gangs. Hisui stages the whole attack under the guise of a bunch of school kids rioting, Yata and Fushimi try to escape the chaos and suddenly Fushimi is pushed down and Yata is grabbed by some big enforcer type. That’s when Mikoto shows up out of nowhere and takes the rival guys down, saving Yata and Fushimi in the process. Yata’s thankful but really confused as to why Mikoto’s there, which is when Kusanagi walks over looking all sheepish as he says he supposes Yata’s their boss now.
Upon learning that he is apparently heir to a giant gang Yata’s super confused but also maybe a little excited, like he always wondered about his dad and learning that his dad only left because he wanted to keep Yata and his mom safe makes him really happy. He’s upset to learn that his dad died recently though and totally out of his element when he realizes that suddenly he’s expected to take over when he has no idea how to do things. He tries to lean on Fushimi a bit for help, since Fushimi knows everything, but Fushimi’s having his own crisis now that he knows Yata’s also part of the yakuza and a rival gang at that, like surely his people know who Fushimi is and they won’t let him stay by Yata’s side (ooh for extra angst points maybe it turns out Niki killed Yata’s dad but sustained wounds himself that killed him, the whole ‘disease of the internal organs’ thing was a cover up). Fushimi also feels like he must be useless to Yata now since Yata has this whole group of people at his beck and call and won’t Fushimi just be a liability, especially since jungle’s started making more moves to destroy Yata’s gang. Fushimi instead gets lured away by another one of the gangs, led by Munakata, believing that by working outside Yata’s group he can actually keep Yata safe, like he believes Munakata can keep Hisui in check and counter any reckless moves Yata might make. Yata of course can’t believe Fushimi left him and is blindsided when he’s informed that in the yakuza, betrayal generally means death and is Yata willing to kill Fushimi for his disloyalty (short answer: nope, no, not happening).