Seonghyeon, the older boy who lived next door and had always cared for Yeonwoo, returns to Korea after a decade. Instead of the warm welcome he anticipated from Yeonwoo, he finds himself met with avoidance and an uncomfortable distance. Hurt by this, Seonghyeon drinks excessively and makes his way to Yeonwoo’s home. Following an unusual noise from within, he opens a door to find an unexpected sight. "Baby… why do you have a vagina?" He uncovers the secret that Yeonwoo has kept hidden for so long. Fearful that Seonghyeon will despise him, Yeonwoo trembles with anxiety. However, when Seonghyeon embraces and reassures him instead, Yeonwoo gradually begins to open up. From that moment onward, their bond grows deeper and eventually becomes romantic. Yet, their tranquility is short-lived. A stalker aware of Yeonwoo’s secret starts to invade their peaceful existence, thrusting them into a perilous new situation—and endangering the life they have built together.