Complex sentence: Masa (this is the name that he performs under, not necessarily his real name) is a Japanese musician and while he is not so prominent in the Japanese music scene, he has been a member of GacktJOB, Gackt's band.
Split into simpler sentences: Masa (this is the name that he performs under, not necessarily his real name) is a Japanese musician. While he is not so prominent in the Japanese music scene, he was member of GacktJOB, Gackt's band.