Seo Hae-young, the only light of Yoon Hae-won, who has no money, no family, and no future.
After Ko Tae-gyeom, his "friend", reveals his feelings for him, Hae-won's life begins to fall apart.
Tae-gyeom demands a relationship through threats, Hae-young wields violence in an unknown manner, and another friend Joo Hyun-woo joins the ranks...
The broken relationship between the four people, the memories of the past that are now faded.
Who will win the irreversible game?