Hero Theo, destined to defeat the succubus Twiska, possesses light blue hair and green eyes, maintaining a youthful appearance. His latent power awakens when Twiska attacks him, revealing his reincarnation as the legendary hero who once defeated the demon king. This heritage grants Theo the ability to transform into an aggressive, sexually dominant persona specifically when confronting demonic threats like Twiska.

During her assaults on villages where she intends to drain Theo's life energy, Twiska finds her plans complicated by his unexpected sexual prowess and youthful look, creating conflict in her objectives. Theo's transformation consistently surfaces during their encounters, even when Twiska attempts to conceal her demonic aura to approach him undetected. This aggressive state neutralizes her succubus abilities, leaving her physically overwhelmed. The transformation significantly impacts demons attempting to kill or seduce him, countering their powers during these confrontations before retreating once the demonic presence subsides.