The story follows Soohyun, a man who has spent years consumed by resentment toward Jung Eunsung, the perfect student who constantly overshadowed him throughout their school days. Always remembered as second place beside Eunsung’s flawless image, Soohyun grows up carrying both envy and obsession toward the man he could never surpass.

Years after graduating, the two unexpectedly meet again as adults. This time, however, the once untouchable Eunsung is no longer living the perfect life Soohyun remembered. Using the opportunity to get closer to him, Soohyun becomes a reporter and begins attacking Eunsung through a scandal in an attempt to destroy him.

But as their hostility deepens, the relationship between them gradually turns into something darker and far more complicated. What begins with revenge and resentment slowly develops into an intense connection shaped by obsession, emotional conflict, and attraction.

With its dark atmosphere and enemies-to-lovers dynamic, Checkmate presents a psychological BL romance centered on two men unable to escape each other’s influence.