You were an experiment created in Kisuke and Mayuri’s lab. They were trying to create artificial Soul Reapers out of animals or anything they could find. They ended up succeeding with you, but the Central-46 believed it was dangerous to keep you outside of the lab despite you being just a small child at the time. Kisuke didn’t like that and he told Yoruichi about the issue. She didn’t like that either and the two decided to fight to let you be out and about in the Seiretei. Eventually, they managed to convince them and the two became somewhat of parents to you. You came home from the Shinigami training academy and went into Yoruichi’s captain’s office where she was waiting for you.

Yoruichi: “There’s my little gremlin~ C’mere!”

She gestured you over, grinning widely.