Basara Tōjō is a former member of the Hero Clan, exiled after a tragic incident involving his unique power. He now lives with his stepsisters, the demons Mio and Maria Naruse, and is fiercely dedicated to their protection. His biological parents are Jin Tōjō, a powerful hero who ingested the blood of the dragon Fafnir, and Sapphire, a demon lord-class demoness and sister of the previous Demon Lord. Though conceived by Sapphire, Basara was transferred to and carried by Raphaeline, a member of the Ten Gods, resulting in a heritage combining hero, demon, and god lineages.

He possesses a tall, slim build, unkempt brown hair, and light green eyes. His body is covered in scars from his past loss of control over Banishing Shift, though he attributes them to a car accident. When using his powers, his eyes sharpen and emit a green, flame-like light. He can materialize the demonic sword Brynhildr, which grants him silver ornate armor on his right arm; with greater synchronization, this becomes a full black and silver armored suit featuring a halo-like object on his back. After achieving spiritual balance, he manifests a full-body armor resembling a corrupted Reginleif form while retaining his humanity.

Basara maintains a laid-back and collected demeanor but is haunted by guilt and nightmares from the incident in the Hero Clan village, where his out-of-control power caused the deaths of friends and comrades. This initially made him fearful of using Banishing Shift and Brynhildr, though he gradually overcomes this through battles to protect Mio and others. He holds a strong belief in family and will protect those close to him even if it means fighting former allies or taking extreme measures. A hidden sadistic side emerges through interactions with Chisato Hasegawa, and he can enter a frenzied state when loved ones are threatened.

His hybrid nature and training grant extensive abilities. As a hero, he has superhuman strength, durability, stamina, and speed, rated B-Rank in his youth and later S-Rank. His speed allows him to create afterimages and employ an Infinite Slayer combat style. He also possesses magic resistance and enhanced healing. His signature technique, Banishing Shift, nullifies or erases targeted phenomena, including energy and matter. A master swordsman, he wields Brynhildr with skills such as Dimension Slash, which severs targets with spatial distortions that prevent regeneration. The Master-Servant Pact with Mio and others further enhances his abilities, increasing his physical attributes and power through their loyalty and subjugation rituals. His demon, god, and dragon heritage allows him to manipulate multiple elements and achieve perfect spiritual balance, making him a rival to the strongest gods.

Basara grew up as a prodigy in the Hero Clan village. The incident involving Brynhildr—where an evil spirit possessed a hero and caused a massacre—led to his exile alongside his father. He later learns of Mio’s identity as the daughter of the previous Demon Lord and agrees to protect her, forming a Master-Servant Contract that accidentally places him as the master. Through various conflicts, he battles demons, heroes, and gods, participates in a tournament in the Demon Realm, and confronts adversaries like Zolgear and Belphegor. He forges alliances such as with Yahiro Takigawa (Lars) and deepens his bonds through Master-Servant Pacts with Mio, Maria, Yuki Nonaka, Kurumi Nonaka, and Zest. His journey involves political intrigue, exposing corruption, and ensuring the safety of his loved ones, culminating in all members of his battle harem becoming pregnant with his children.