Yusilmul

Seo Yi-Hwan, the youngest daughter of a conglomerate. She, a close friend, and a world-renowned pianist have enjoyed dangerous times committing themselves to promiscuous parties and drugs together. But soon, the walls of trust they've built slowly begins to crack as the mysterious girl, Yoo Se-Rin appears in the lives of the two men. Who is is this new mysterious girl?

(Source: Ridibooks, translated)