Chigusa Iinuma is the widow of Seijiro Iinuma, Japan's deceased Prime Minister, and holds social prominence as the former First Lady. Her primary narrative involvement occurs when she confronts Akira Takizawa publicly at the airport upon his return to Japan. She accuses him of disgracing her late husband's legacy, insists on a DNA test to verify Takizawa's claim of being Seijiro's illegitimate son, and places him under temporary custody pending a hearing on alleged terrorism plots.

Her actions throughout these interactions are fueled by deep frustration and anger toward Takizawa, whom she blames for her husband's death. Later, when Takizawa and Eden group members visit the Iinuma residence, Chigusa again questions Takizawa about his motives for asserting paternity. During this encounter, her confusion and exasperation are evident, heightened by her lack of participation in the Seleção game and her unawareness of its rules or the underlying conflict involving figures like Mononobe.

Chigusa serves as an obstacle for Takizawa, embodying societal authority and the personal stakes tied to his mysterious past. The resolution of the paternity question remains ambiguous within her onscreen appearances, leaving her perspective unresolved.