In the opening episode, ordinary student Mizuki navigates daily life under the watchful eyes of his two remarkable older sisters. Cool student council president Ema enjoys lightly teasing him, while idol-like Ryuka keeps him busy with small errands. When Mizuki suddenly finds himself with a girlfriend, the sisters sense a shift in his world and begin to engage with him more closely. Yet when that new connection falters and leaves him downcast, Ema quietly decides to step in with unexpected warmth.