Seo Jeong‑ha is a fourth‑year university student. She decides to sell a speaker her ex‑boyfriend gave her on a secondhand marketplace. The reason is simple: now that she has a handsome and sweet almost‑boyfriend, Park Min‑jun, that speaker has become nothing but a nuisance. But when she goes to complete the sale, the buyer who shows up is… her ex, Choi Seo‑hun. “Do you know how much this cost? And you’re selling it for just 180,000 won!?” Thus begins a romance drama where a three‑way relationship kicks off from a secondhand transaction.