Basara Toujou is a high school student and exiled former member of the Hero Clan. His banishment followed a crisis five years prior where his Banishing Shift ability went out of control, causing accidental deaths that left him psychologically scarred yet maintaining a calm demeanor. His combat prowess relies on extreme speed and the power-nullifying Banishing Shift technique, wielding the cursed sword Brynhildr.

After his father's remarriage, Basara assumes the role of protector for stepsisters Mio Naruse, a Demon Lord heir, and Maria Naruse, a succubus. An accidental reverse master-servant contract binds them, with Basara as master. This contract punishes disobedience with aphrodisiac effects requiring physical contact to resolve, complicating their daily lives. He later forms similar pacts with other allies, including childhood friend Yuki Nonaka, to bolster their strength. Protecting those he cares for is his core motivation, driving confrontations with demonic threats and his former Hero Clan.

In *Departures*, Basara confronts his past before returning to the Hero Clan village, testing his resolve in combat against ally Takigawa Yahiro and affirming commitments through intimate moments with household members, including a symbolic wedding dress scene. His relationship with school nurse Chisato Hasegawa deepens during a hot springs date where they discuss his resolve and family history.

By the series' conclusion, Basara marries multiple members of his extended household—Mio, Maria, Yuki, Zest, and Chisato—all of whom later bear his children. This marks his evolution from isolated exile to the center of a forged family united by loyalty and mutual protection.