Seiko Kotobuki

Is a friend and former love rival of Risa Koizumi's. She is a support character in both the original and sequel mangas, and the anime. Seiko is a genuinely cheerful person, but does have a side of her that is impulsive and jealous, and she lacks a tolerance for Haruka's stupidity. Seiko's impulsive nature causes her to act without thinking, notably when she forces a kiss on Ōtani in front of his friends before ever having talked to him.