Riko's old friend from the cram school and the Vice President of Minami Middle School's Student Council. He tutored Riko for her entrance exam in Fujisaki Middle. He is also the romantic interest of Natsuo Maki.
During his childhood, he didn't have many friends and was often badmouthed due to his serious personality. He became friends with Riko when she asked him to tutor her for the Fujisaki entrance exam. He is one of the few people who know the reason why Riko wanted to enter Fujisaki Middle.
Riko was the one who gave the nickname "Yan", apparently coined from his real name which transformed over time. According to others, it was after his time with Riko that Yan started to mellow down.
They both finally met again in volume 2 of the manga and episode 6 of the anime.
