Mirei is a devoted little sister who firmly believes her older brother is her ideal type and is seriously planning to marry him in the future. The brother, too, has always enjoyed going on dates with his cute sister, sleeping together, and bathing together as if it were perfectly normal. But recently, after friends told him "this kind of relationship is weird," he began feeling embarrassed by her affectionate behavior and started treating her coldly. This sudden distance made Mirei anxious—was her brother starting to hate her? Heartbroken and sad, she sneaks into her brother's room, determined to become the type of girl he truly desires. There, she discovers a fashion magazine featuring an adorable girl dressed in a ●○■★ suit. Could it be? Does her brother actually prefer girls like this? Inspired, Mirei puts on a similar ●○■★ outfit and uses her newly acquired erotic knowledge from the internet to launch her "Make My Brother Obsessively In Love With Me" plan. However, Mirei is still a virgin with no real sexual experience. As the plan unfolds, she subjects her brother to bondage, cumshot control, forced ●○■★ drinking, and even aggressively demands incestuous sex, pleading, "Big brother, take my virginity!" Of course, he's not allowed to cum freely. Finally, to completely claim her brother as her own, she takes the initiative to take his virginity herself. This is the slightly twisted story of a pure-hearted little sister who loved her big brother too much.