Ren Kurogane leads the idol group HY:RAIN. Her surname "Kurogane" signifies "black gold" or "iron," while "Ren" means "lotus" or "water lily." She possesses blue eyes and waist-length blue hair.

Ren shares a complicated history with Haru Nabatame, being childhood friends and former classmates who initially pursued idol careers together in HY:RAIN. Their relationship strained after Haru left the group. Ren voiced disappointment over the departure and actively sought Haru's return, often framing her motivations with the catchphrase "Since I'm better than Haru." This dynamic fostered unresolved tension, with Ren harboring significant guilt over her role in driving Haru away. Her regret fuels a persistent desire to reconcile and restore their partnership.

Her personality blends stoicism with intense dedication, though interactions involving Haru reveal deeper vulnerability. An episode titled "Ren Kurogane Wants to Go Back" reflects her emotional journey and regret concerning their fractured friendship. While generally composed, matters tied to Haru expose layers of remorse and determination.