Ranmaru Kurosaki's siblings are coming to live with him. While his older brother Rush is ecstatic about the situation, his little sister Arisu is the complete opposite. She now has the daunting task of taking over Nanami Haruka's job as a composer for STARISH, plus becoming their lyricist. Being stoic by nature, she could care less about the boys flirtatious ways, including from HEAVENS and Quartet Night. However, as the Kurosaki family's past starts to come back and haunt her, she realizes that these boys are the key to protecting herself from her older brothers' mistakes. Yet through all that goes on, she asks herself one question. Is it too late?