Shigeru Mitsuishi

Shigeru is Seiichi's cousin.

Personality
At the beginning of the manga, Shigeru seems to be a friendly kid. He enjoys playing games with Seiichi and exhibits intrepidity, standing at the edge of a cliff without fear. Shigeru is a bit immature, as he became angry at Seiichi for not wanting to stand at the cliff with him. He is also careless, nearly falling off the cliff because he was dancing there.

After the cliff incident, Shigeru is lost. His old personality is completely gone, Though, later on, he is aware of the change. He verbalized to Seiichi that he missed his old self.