Kōtarō Tatsumi, originally surnamed Inui, attended high school in Saga Prefecture around 2008 as a shy and serious classmate of Sakura Minamoto. Driven by Sakura's forgotten dream to become an idol and a prophecy threatening Saga's eradication, he adopted his new identity. He connected with a bartender later revealed as the immortal Jofuku, who guided their plan. As Franchouchou's producer, he resurrected seven deceased girls from different eras as zombies, using necromancy and expert makeup to disguise their undead nature for the "Zombie Land Saga Project." His goal was to revitalize Saga through regional idol performances. He initially presented himself as loud, eccentric, and arrogant, frequently wearing a black jacket draped over his shoulders, a red vest adorned with dried squid tentacles, and dark sunglasses hiding his eyes. His management style was impulsive and demanding, often forcing performances in unsuitable venues like death metal festivals and ignoring the girls' feelings or logistical realities. Beneath this persona, he struggled with public speaking, insecurity, and intense project stress causing physical symptoms like stomach pain. Following Franchouchou's disastrous EFS Stadium performance in Season 2, resulting in massive debt and plummeting popularity, he hurtled into severe depression. He isolated himself, neglected his appearance, grew out his hair, and drank heavily. He only recovered after a pivotal conversation with Jofuku, returning to support the group during a critical performance. Failures and interactions with the girls spurred his development. After the EFS incident, he became more reflective and responsible, prioritizing the group's well-being over his ambitions. He demonstrated genuine mentorship: composing a song for Lily to reconcile with her father, advising Saki against violence to protect Franchouchou's reputation, and excluding Ai from an Iron Frill collaboration to foster the others' independence. His relationship with Sakura significantly improved, culminating in a heartfelt promise during Revenge's finale to support Franchouchou's dream of global recognition. His skills extended beyond management: he was a capable beatboxer and rapper, provided musical accompaniment during performances, and wrote songs like "Atsuku Nare." He handled business negotiations, publicity, and crisis management, though his earlier impulsiveness often undermined these efforts. Manga depictions showed his behind-the-scenes work securing sponsorships and scouting Saga locations, highlighting dedication amidst ongoing stress. The fight against Saga's curse intensified in Revenge. After a natural disaster destroyed their home and nearly exposed the girls' identities, he reaffirmed his commitment. His final arc showed him coughing blood—a physical manifestation of the curse's toll—yet persisting in his pledge to ensure Franchouchou's success.