Mitsuru Tsutsui, husband to Kie and father to Hikari and Kaoru, navigates familial tensions shaped by his passive demeanor and aversion to confrontation. When Kie files for divorce, suspecting infidelity with a colleague named Kono, the crisis stems from a misinterpreted dinner encounter—Mitsuru had rebuffed Kono’s advances, yet his reluctance to assertively clarify the situation fuels mistrust. Their reconciliation underscores his quiet dedication to mending familial bonds, prioritizing dialogue over self-defense despite his tendency to assume others will dismiss his explanations.

Professionally, Mitsuru channels his introverted nature into meticulous work as an adhesives researcher, though his high blood pressure and social reticence complicate personal interactions. These struggles mirror his son Hikari’s communication difficulties, framing shared vulnerabilities within the family dynamic. A temporary estrangement during the divorce proceedings tests their relationships, yet resolution emerges through candid conversations, emphasizing Mitsuru’s understated loyalty.

His narrative arc explores the fragility of trust and the quiet resilience required to sustain connections, illustrating how unspoken assumptions and health-related stressors can strain even deeply rooted commitments. The resolution hinges not on dramatic confrontations but on incremental understanding, aligning with Mitsuru’s character—a man who navigates conflict through patient endurance rather than overt assertion.