In the tumultuous world of demons, Basara Toujou shoulders the responsibility of protecting his demonic step-sisters from the covetous beings of the underworld. As life unfolds, Basara, alongside Mio and Maria Naruse, strives for a semblance of normalcy post previous upheavals. Yet, tranquility remains elusive as fresh challenges emerge, drawing Basara and his companions into a whirlwind of peril. Amidst this turmoil, the unexpected arrival of Maria's elder sister, Rukia, disrupts their fragile stability, beckoning them to the demon realm.