Yuuji Kikuchi (菊地 悠司 Kikuchi Yūji) is a character that shows up especially in the manga extras. He's childhood friends with Maki Tokitou and his family owns a public bathhouse, which Kenta Usui and his mother often go to.
He was a classmate of Karin, who seemed particularly excited for the school festival. However, during the preparations, he was attacked by Karin's grandma, who was getting blood for her husband. He still managed to attend the festival. He originally had a crush on Fumio Usui and wanted to confess, but due to unseen issues he is unable to. Later Maki attempts to cheer him up, Yuuji then asks to date Maki. She replies that he would need to be strong. Eventually they get married. The two supposedly fight often, even on their honeymoon they also have a daughter and son called ryujji and taika