Ichikawa is a very weak looking student. Yamaguchi believes he's in the 2nd year class, at Shirokin Academy. He's one of many boys that she wanted for her choir club, though besides her preference towards look. Her other reason was tied down more to her past.
Ichikawa is by all appearance a good kid, but its clear he has not so good friends. Though he never complains, he clearly is weaker compared to his "friends", who use him as their punching bag when they wanna test wrestling moves. Miss Fujiyama constantly tries to get him to join the choir club, but to no avail. After another failed attempt, Fujiyama reveals to Yamaguchi why she's so insistent. When she worked at a middle school, a student of hers was in a situation very similar to Ichikawa's. And that student had tried to commit suicide due to the bullying.
Fujiyama hopes that getting Ichikawa in her choir club, will at least shield him from those thoughts and probably those that bully him.
Without realizing, Yamaguchi's class is shocked to see Ichikawa on the roof and over the rails. All are worried he's about to commit suicide. Fujiyama is able to distract him, while Yamaguchi runs up to stop him. While talking he admits he wasn't planning on doing anything, he just found himself there without realizing. After talking, Fujiyama pleads with him to go back over the rails. But before he can he nearly falls, but is caught at the last minute by Yamaguchi.
Though she almost joins him, until Shin and the others are right behind her and grab her before they can fall. Fujiyama is relieved to see Ichikawa is alright. He's later shown as part of her choir club.
Ichikawa's story is the same in the anime version, there are more scenes added given the time slot of the show.