Fabricated past

Shuichi's parents are a famous actor and a screenwriter, who went overseas for business, which is why Shuichi began to live with his uncle and his wife. While Shuichi claims there isn't any sad story behind it all, his parents are neglectful towards him, and he smiles bitterly whenever he talks about them. To show his gratitude to his uncle, Shuichi helped him by working as his assistant in his detective agency. While he was only helping out and had no desire to be a detective himself, he learned to be a detective this way. Shuichi's first detective case was unofficial but a tough one, as his classmate asked him to find her miniature pet alligator, and he had to do a lot of research, prepare tools and eventually climb around mountains and swim up rivers. As thanks for finding her pet, Shuichi's classmate later gave him chocolate for Valentine's Day, though he assumed it was done just as friends. Shuichi was mostly happy to be useful and memorized her words "thank you". His first official case was an infidelity case, which was nothing compared to the alligator one.

Most of the cases that happened to come to his uncle were small things like investigating infidelity, but on the one rare occasion, Shuichi managed to solve a murder case faster than the police and became publicly known as the junior detective, gaining him his Ultimate title. However, Shuichi does not believe he deserves the title, claiming that he only happened to solve this one case by chance.

In reality, the situation was more complicated. When the culprit was captured thanks to Shuichi, his eyes were full of hatred and malice as he looked at Shuichi, and the boy never forgot that gaze. Shuichi heard later that the culprit had killed the victim to avenge his family and the victim was a horrible person who had tricked the culprit's family and driven them to suicide. Shuichi felt guilty for "siding with" the victim and felt everything was his fault because he exposed the truth. He gained a fear of exposing the truth, considering himself a pathetic detective, and he began to wear a hat because he couldn't look at other people's eyes anymore.