Tenma Tsukasa
Tsukasa was born to the Tenma's, an upper middle class family, he was the oldest of 2 children. Saki, his younger sister, struggled with chronic illness. Tsukasa adores Saki and always wanted to protect her, but since he couldn't actually help with her illnesses, he focused on keeping her safe. It started off with him just being protective of her when around strangers, but slowly turned into a fascination with criminal science. This led Tsukasa to wanting to work as a detective, which when he was finally old enough to leave the house, he did. The issue was while he was well read up on criminal science, and felt confident in his abilities, people around him doubted him. Despite trying to find work at several agencies, they all turned him down. He decided he didn't need them, and that he could prove them wrong by being a self employed solo detective.
For several months, no one hired Tsukasa, forcing him to get a job at a local shop, but he still didn't give up. Finally half a year after putting up flyers, someone called him to hire him for an investigation, it was his kind elderly neighbor. He figured she was probably just hiring him out of pity, but he was still willing to take on her case with everything he had. After learning it was just her dog going missing, he felt the case would be easy. However after days of searching, the only clue he found was the dog's torn collar.
While continuing his investigation, he caught the eyes of Shiraishi An, an actual experienced, professional detective. She was investigating a missing persons case, and noticed Tsukasa was in a lot of places she had investigated. After ruling out him as a suspect, she learned of his own investigation, and the similarities made her strike up a conversation.