A new apartment. A cheap rent. A fresh start. That's all Dunk Natachai wanted after his breakup. But the neighbors aren't just strange - they're unsettling. Smiling too wide. Watching too closely. Calling him things he never told them. And next door lives Joong Archen. A man who never leaves traces. A name whispered in FBI files. A ghost who shouldn't exist. Dunk's best friend swears it's safe. Dunk wants to believe him. But when the walls feel too thin, the hallways too quiet, and the neighbors too interested... He realizes he didn't move into a home. He stepped into a cage.

Joong is a world-famous boxer - brutal in the ring, worshipped by fans, but hollow inside. He spends his days training, fighting, and bleeding under the lights, with nothing soft left in his world. Dunk is a pianist and part-time music teacher who rents a studio in the same building as Joong's gym. He doesn't follow sports, doesn't know who Joong is - only that a tired, bruised man keeps lingering by the door after practice, listening to the music he plays. At first, they're opposites: fists vs. keys, violence vs. art. Joong doesn't talk much, but Dunk starts noticing the way he always comes back, sometimes still bleeding, to sit quietly and listen. What begins as silence slowly turns into something deeper - Dunk teaching Joong music as a way to control his rage, Joong teaching Dunk about endurance and discipline. But their worlds clash when Joong's violent career threatens Dunk's quiet life. Dunk sees the man behind the fighter, and Joong starts to wonder if he can be more than just blood and fame - but the cost of being with him might destroy them both.