The Deepest Serenade is a Manga/Manhwa/Manhua in english language, CRIME series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

Ritsu, a junior high school student who lives in his parents’ home with a piano teacher, is pulled into a spiral of passion after a performance by a new piano student, Saya.