Wataru Izutsu is married to Rina Izutsu. Upon discovering her affair with Junpei Takamori, he confronts Junpei violently, leaving him visibly injured. Wataru then directly informs Azu Takamori of the infidelity, causing disruption in both marriages.

His reaction to the betrayal involves controlling behavior and physical aggression toward Rina, including an act of marital rape. These actions stem from deep-seated insecurities and a volatile response to betrayal. He actively investigates the affair and takes decisive steps to address it, contrasting with other characters' indecision.

After the affair's exposure, Wataru separates from Rina. This separation marks the start of personal development where he shoulders full parental responsibility for their children as a single parent. His efforts to rebuild the relationship lead to the children choosing to live with him in Tokyo, reflecting reconciliation and growth in his paternal role.

Wataru also implements practical measures to protect his family interests, such as changing locks to secure his home following the marital breakdown. His character shows a complex path from initial rage and violence toward a more focused, though still flawed, commitment to his children's well-being post-separation.