Kōta Kunieda

Aoi's younger brother and Baby Beelzebub rival who beats him at everything. Kōta is the reason Aoi created her alter ego, Aoi Kunie, so that nobody sees her taking care of a baby, however the mothers at the park recognize her and believe Kōta is her child.

He is often comedically presented as Beel's rival, constantly outdoing the future demon king in anything he attempts, which usually results in Beel crying and shocking Oga, who is usually unaware of what has transpired.