During a trip to a hot springs resort, the tension between Akitsuki and the prickly Airi reaches a breaking point. After a series of provocative encounters fueled by a mysterious aphrodisiac, Airi reveals her deep-seated insecurities and her longing for her father's genuine affection. Following a night of passionate intimacy and mutual confession, Airi wakes up with a blackout, leaving her oblivious to their shared secrets just as Marina arrives.
During a family getaway to a hot spring, a sudden bout of memory loss leaves Airi in a childlike state, leading her to call her sister Marina "Mama." Taking advantage of the confusion, the father indulges in forbidden encounters with Marina, unaware that Airi's memories have already returned. After a brief moment of emotional turmoil and a near-departure, the truth comes to light, and the family returns home with their twisted bond stronger than ever.