His rejection and given nickname drove him to harass Aki one day and harms Masamune who was protecting her.
Akio is a boy who looks smart. He wears the Yasaka High School uniform, and also has glasses. In the manga, he does button his coat, but leaves it unbuttoned in the anime.
Akio seems to be nervous, as any boy would, when he is waiting to hear Aki's answer to his proposal. When he is rejected, he feels doomed as if his life has ended in failure. Akio can also be impulsive when he decides to attack Aki for revenge when he was given a nickname.
In Chapter 1, Akio is introduced as a boy in Masamune's class who wrote proposed to become Aki's boyfriend in letter form. She visited Class 2-B to shoot him down and give him a nickname.Some time later, he wanted to get revenge on Aki for humiliating him in front of Class 2-B. Akio decides he will cut her hair, only to have been foiled by Masamune. Akio snaps out of his hatred for Aki and realizes what he was about to do before running off.
In the anime, Akio sees Masamune the next day with his injured hand and apologizes for what he did. Girls around the two wonder what happened, but Masamune keeps it a secret, creating different implications of what went on between the boys.