Takeru Aizawa is the younger brother of the Aizawa sisters. He is one of the first kids to play with Squid Girl, he seems to like her, even going as far as to act like a squid so she will play with him. He also gave her the the nickname Squid Girly. Within the series he shows some signs of a crush on Squid girl, notably in a later episode when she calls him boring. He becomes very sad, saying "My heart is breaking."
Takeru Aizawa has many characteristics like any young boy. One of the first episodes he shows his jealous side, getting mad when he sees squid girl "playing" with Eiko. Later in the series he is seen being sweet, not joining in teasing with his friends and usually saying nice things. But like any kid he show no sense of what would be perceived as gross, eating Squid Girl's squid ink pasta without thinking twice, even after having seen how she produced it (although Chizuru did the same). He also shows signs of being a scaredy-cat, this was shown when he was beyond scared of a tv show on episode 3. He was the only one that showed real pain when Squid Girl tried to be human, hating her new self saying its not her and even started crying.
Takeru has spiky black hair and gray eyes. He is usually seen in a green shirt with "GO!" or a different one on it and a pair of tan shorts as well as green low top sneakers. On occasion he is also seen in blue swim trunks. He is shown to be "pretty" when he puts on womans make up.