Waves Upon Waves

There's a long-held legend in Seol-Yeong's family: if nurtured with true love, the Manpasikjeok will transform into a human. The realistic Seol-Yeong, disbelieving her family's legend, decides to sell the Manpasikjeok. At that moment, the Manpasikjeok transforms into a human, granting Seol-Yeong's wish. A miraculous instrument, a girl who doesn't believe in miracles, and a twisted romance between two men and women(?) with conflicting views.

(Source: Naver, translated)