Mahiru Oki embodies Ebisu, one of the Seven Lucky Gods, as part of the Better Fortune Research Organization. She constantly carries a fish, honoring her link to Ebisu—deity of fishermen and fortune. This connection manifests in her transformed state through a weapon shaped like a fishing pole with an attached fish. As the sole university student in the club, she holds the position of oldest participant in group activities. Her duties include fighting Magatsugami, monsters that devour negative emotions and inflict misfortune, alongside fellow Happy Seven members.