Kiyohiko is the childhood friend of Emi who always teases him. When Emi mistakenly kicked Hidenori into the river, Hidenori concluded that she must have been kicking Kiyohiko a lot and that he should do the same thing to Emi in retaliation. He cried, claiming that Hidenori is the first person who understands what he feels. After this, the three became friends and they spent the rest of the summer vacation together.