Yorimichi has played with Yuni since he was a baby. When he was younger, he wanted to become good at shogi and often went over to his grandfather's house to get lessons. He would also sometimes watch over and play with Kimichika Haijima and Yuni when they were little. As he got older, he became a delinquent and subsequently got abandoned as a lost cause by his relatives, but Yuni knew he had his good points and continued to hang out with him, even when he knew Yorimichi was sponging money off of him.
