Captain Ei Domon commands the advanced submersible-space vessel *Blue Noah*, a role demanding profound personal sacrifice. He chose duty over family, departing his wife and daughter during her terminal illness to oversee *Blue Noah*’s development—a choice that cemented lasting estrangement from his daughter, who blamed him for his absence in her mother’s final moments.

Before the alien invasion erupted, he spearheaded testing of *Blue Noah*’s sister submarine, *Tempest Junior*. After encountering the teenagers who activated *Blue Noah*, he integrated them into his crew, assigning roles aboard *Tempest Junior*. His command prioritizes strict discipline and calculated mission hierarchies, diverting resources to dismantle alien gravity control bases ahead of enhancing *Blue Noah* for interstellar missions.

A pivotal backstory reveals his decision to cancel leave, mistakenly believing his wife’s condition had stabilized. Her sudden passing during his absence deepened his daughter’s resentment. During the voyage to Bermuda, he confronts these unresolved tensions when his daughter briefly joins the crew, though their fractured bond persists.

His leadership extends to mentoring young recruits like Shin Kusaka, preparing him for increased responsibilities. In combat against alien forces, his strategies—such as deploying the Anti-Proton Gun—focus on achieving objectives with minimal human loss. His unwavering, duty-focused resolve remains static throughout, balancing military precision with unresolved personal strife. The character’s portrayal is confined to the original 1979–1980 television series, with no documented expansions in official media.