Ruka is an idol under Tsukino Productions. He is a member of the unit ROCK DOWN, which is part of VAZZROCK.

Ruka is highly unpredictable, except to Gaku, and can be a lot to handle at times. He enjoys the attention he gets and cannot stand to be alone. His acting skills are amazing, but once in character he gets stuck in character for a period of time. Ruka is fun loving and social and loves to be active.

(Source: Tsukipro Wiki)