The protagonist awakens with memories of a past life, realizing he has been reincarnated into the world of an adult-rated erotic game. He is now in the body of Kasajima Yuuji, a character destined to be an antagonist. His primary goal is to avoid the beautiful sisters, whom he remembers as dangerous figures from the game. Initially, he tries to maintain distance, but finds himself drawn to them and inadvertently gets closer to the protagonist. During a school trip, he witnesses the younger sister of the beautiful pair involved in a minor dispute and later, a fabricated incident where she is framed for losing money. He manages to resolve the situation temporarily.
The younger sister attempts to thank him, but he tries to refuse. Later, he observes the protagonist with another girl, while the elder sister of the beautiful pair is by his side, making him nervous. The protagonist develops feelings for someone other than the sisters, which prompts them to seek his advice, clearly intending to win him back. They also express a desire to properly thank him.
A traumatic flashback reveals the protagonist's past life memories of playing the game and witnessing the cruel fate of the antagonist, Kasajima Yuuji, who was physically and mentally tortured by the sisters. He realizes he has become this very character. Upon checking his surroundings, he finds an enrollment guide, indicating he is before the school entrance ceremony and hasn't yet interacted with the sisters or the protagonist. He resolves to live a safe, uneventful life to avoid the game's bad ending.
As Kasajima Yuuji, the son of a wealthy family, he lives in a luxurious apartment. The day before school starts, he meets his dedicated and beautiful maid, Hibari. He learns his parents will be absent from the entrance ceremony. He attempts to interact more casually with Hibari, but his efforts are met with her stoic demeanor. The next day, he is driven to school in a limousine by Hibari. At school, he overhears students discussing his reputation as a playboy and someone involved in illicit activities, confirming his low popularity.
The beautiful sisters, Sumino Mahiro (a popular model) and Sumino Riina (with a more provocative personality), arrive, drawing significant attention. They encounter the protagonist, Saeki Yuuto, who is surprised to see them at the same school. It is revealed the sisters deliberately enrolled to be near Yuuto. Yuuto, portrayed as naive and oblivious, is easily drawn into their orbit, much to the envy of other male students. Yuuji, observing this, vows to stay away from the sisters.
During the entrance ceremony and the first class, Yuuto is constantly surrounded by the sisters, creating a spectacle. Yuuji, in his back-row seat, is also isolated due to his intimidating appearance and negative rumors. The class decides to have a get-together, but the sisters decline to spend time with Yuuto instead. Yuuji leaves, feeling he accomplished nothing.
Later, Yuuji has a disturbing nightmare of the sisters' torture. He goes out for air and encounters Yuuto at a convenience store. Yuuto, friendly and trusting, invites Yuuji to talk. Yuuji, panicking about how to interact without attracting the sisters' attention, tries to navigate the conversation. He accidentally calls Yuuto by his first name, which pleases Yuuto, who explains his lack of male friends. Yuuji decides that gaining Yuuto's favor might be his best chance of survival. However, Yuuto then declares he will introduce Yuuji to his "best friends," Mahiro and Riina, leaving Yuuji in despair.
The next morning, Yuuji tries to avoid school, but Hibari insists he attend. He is driven to school and immediately faces more negative gossip. Yuuto intercepts him, excited about their friendship. The sisters arrive, and Yuuto introduces Yuuji as his friend. The sisters, uninterested in Yuuji, dismiss him and take Yuuto away. Yuuji is relieved that he wasn't targeted, believing that focusing on Yuuto's favor is the key to his safety.