Yokoi is a girl who sits next to Seki-kun. She always tries to avoid Seki-kun's weird and interesting behaviors, but she unwillingly concerns herself with them anyway. Her hobby is crocheting and she is quite skilled in that. On the other hand, her drawing skills are quite awful and she doesn't realize that. She befriended Toshinari's little sister Jun, and even came to Seki's house to play with her. During parent visitation day she also joined forces with Seki's mother in preventing Seki-kun from playing during class.