The Greatest Detective From East

This is inspired by GriffinLeeroy and KnightRider_35

Inko shimura and yusaku kudo had a one night stand, but they didn't have feelings each other so they remained friends. However, inko got pregnant, so yusaku promised to step up as a baby's father. Sure enough, when izuku was born, yusaku does indeed step up to be a father to izuku

Inko marry her mother's student, toshinori yagi, while yusaku marry yukiko, and of course they know everything

Inko and toshinori had a daughter name izumi, who is half a year younger than izuku. izuku is misdiagnosed as quirkless, however, leading izumi and her friends (most of 1-A) to bully him and try to make him give up being a hero

Inko and toshinori saw this and were furious.They punished the kids that bullied, but they saw izuku was still uneasy/scared around them, so they decide to send izuku to yusaku, who heard about the news and was furious

Years later,izuku back to japan and his family and explain to them that he has a case/mission that nezu gave him which everyone now realized that he is 'the greatest detective from east' with his new name as shinichi kudo,and of course he never forgave his former bullies,especially izumi

After izuku's fight with overhaul and rescuing eri, alas, and myu, nezu gave them a trip to paris to relax/break when they arrive, they greeted by yusaku, his wife, his uncle and aunt, his cousin and some elementery kids who is his friends when izuku turns into a kid and becomes conan edogawa, and his little sister who call him 'oni-chan' which breaks izumi's hearts

Suddenly, a three boys furiously storm up and start yelling at izuku for being so reckless. The girls that use to bullied him about to step in and izuku told them to back off and suddenly ... Izuku hugs them and apologizing for scaring them. The boys calm down and kiss him which lead the girls to a heart breaks

Izuku's former tormentors start to thinking ... What the hell did he do while he was gone!?