Friends And Allies
Haruko is Takeru's childhood friend, and from the beginning of the storyline he addressed her as Haru-nee, implying he sees her as an older sister. He is protective of her, but usually ends up being scolded or beaten by her for the perverted situations he ends up in. He seems somewhat resigned to her constant beatings, never really challenging her on them.
Inaho and Takeru are old friends, though have not seen each other for 10 years. When she was saying goodbye to him as a child, he promised her to be together forever, which led to her falling in love with him. However, he tells her he does not see her romantically when she confesses to him. Despite this, he still considered her to be a extremely close friend.
Takeru and Kengo are partners-in-crime; they first meet and bond while attempting to spy into the girls changing room. As the only male members of Maken-Ki, they tend to suffer together, and seem equally perverted.
Takeru was on bad terms with his father after his mother died, running away from home and going to into a rage upon learning that it was his father that sent Inaho to Tenbi. However, he has since reconsidered his relationship with his father, and wishes to reconcile with him.
Upon their reunion, he claims the reason he didn't want to return home was because the loving overreaction by his father upon seeing him again. He also considers his father a perverted old man (ironic, given his own behaviour).
As a result of his training, Takeru has become quite similar to his mentor in that they both get constantly scolded for their actions. They are also quite close, although some of Minori's rewards (i.e. chances to fondle her) completely deprive him of motivation.
Rivals and Enemies
For the 10 years between his mother's death and the main storyline, Takeru harbored a deep hatred of Tesshin, blaming him for his mother's death. However, after his encounter with Tesshin during the Summer Camp arc and Tesshin's actions, he realises his hatred was his own weakness, and comes to respect Tesshin. He tells Inaho that he is deeply grateful to her father, saying he received many beatings, but they really saved him.