Basara Toujou, exiled from the Hero Clan five years before the main events, lost control of his unique Banishing Shift ability during an S-Ranked Evil Spirit incident. This catastrophe killed multiple villagers, including friends and family, though he spared childhood friend Yuki Nonaka. The trauma initially crippled his power usage. His father Jin Toujou secured his release by renouncing his "Strongest Hero" title, leading them to relocate.

After Jin remarried and departed overseas, Basara gained stepsisters: Mio Naruse, daughter of former Demon Lord Wilbert, and Maria Naruse, her succubus guardian. Learning of Mio's demonic heritage and threats from Demon Realm factions, he chose to protect them despite prior deception. During Maria's forced master-servant ritual, succubus magic reversed the contract—binding Basara as Mio's master. Disobedience triggered intense aphrodisiac effects in Mio, requiring physical contact with him for relief.

Throughout subsequent conflicts, Basara formed similar pacts with allies like Yuki Nonaka to amplify combat strength. He wielded Brynhildr, a sword purified from its curse during his past incident. His high-speed combat leveraged Banishing Shift to nullify incoming magic or skills, an ability born of trauma but mastered through defending his family.

His protective drive extended beyond blood ties, forging bonds with Mio, Maria, Yuki, and allies like Zest. He halted Mio's violent revenge against Zolgear for killing her foster parents, believing it would darken her future. In the BURST arc, he entered a Demon Realm tournament to shield Mio from political turmoil, solidifying his resolve to safeguard his household.

Later official media concluded with Basara marrying eight women from his circle—including Mio and Maria—with several bearing his children, cementing his commitment to familial bonds forged through adversity.