Imaizumi Keita is a first-year high school student whose parents forced him to live alone at the start of his school year. Their stated reason is that he is not manly enough and needs to become more independent. The irony of this arrangement becomes clear almost immediately: instead of learning self-reliance in solitude, Keita's apartment quietly transforms into a daily hangout spot for three popular gyaru classmates. The trio is composed of Hamazaki Reina, a strong-willed and competitive blonde who naturally takes the lead in their group; Sasaki Yukina, an energetic and upbeat girl with long purple hair who is the most openly affectionate and sexually forward; and Kurumizaka Ruri, a calm, calculating girl with light-colored twintails from a wealthy family who often maneuvers to gain an advantage over the other two. At first, the dynamic is casual and friendly, built around video games, snacks, and idle chatter. The tonal shift occurs when Reina, bored with the usual activities, instigates a physical encounter with Keita. The other two girls soon join in, and Keita's home becomes a space for an ongoing sexual relationship among all four of them. What starts as a playful arrangement deepens over time as each of the gyarus begins to develop personal feelings for Keita. Reina shows signs of genuine jealousy whenever he grows close to one of the others. Yukina, who initially tried to keep the arrangement purely physical, starts to struggle with emotional attachment after a warning from her older brother. Ruri, the most pragmatic of the three, begins orchestrating small manipulations, such as engineering seating charts at school or using her social connections to maintain proximity to him. Keita himself is a gentle and unassuming boy, skilled at cooking and housework, who gradually becomes more confident and assertive. The narrative is set primarily in Keita's apartment, with some scenes at school through the lens of the Idol Research Club, where the three girls are members. As the story progresses through its sequel series, Deep, the setting expands. Keita's apartment is condemned, and through Ruri's influence he moves into a luxury unit owned by her father, where Reina's older sister Risa, an adult beautician, becomes his neighbor and eventually a participant in the dynamic. Additional supporting characters complicate the situation further: Keita's older brother Keiichiro, an overachiever who unintentionally fuels Keita's insecurity about his masculinity; Mari Tsutsumi, a glasses-wearing classmate who acts as Ruri's informant and spy; and Keita's mother, a regular client at Risa's salon who worries about her son's social life without realizing the full extent of it. The narrative explores themes of growing emotional entanglement beneath a surface of casual fun, each character's personal insecurities and pasts, and the escalating tension as the girls' genuine romantic interest in Keita strains the group's equilibrium.