In this story, long ago, a young Prince Yosho met a mysterious demon girl named Yuzuha during a special celebration called the Startica festival on their home planet Jurai. Their encounter was filled with curiosity and innocence, but it was cut short when palace guards drove her away, leaving Yuzuha with feelings of resentment and heartbreak towards Yosho. Fast forward 700 years, Yuzuha awakens in the underworld, where she learns that Yosho is still alive and now on Earth, celebrating Christmas with the Masaki family and the women surrounding Tenchi Masaki, who is at the center of this story. Believing that Tenchi is a charming man surrounded by many women, she decides to send him a gift, using a lock of his hair and a piece of herself to create a hybrid girl—part human, part Juraian, and part demon—hoping to amuse herself with mischief.
During a hot summer day, Tenchi encounters a teenage girl named Mayuka, who boldly calls him "daddy," shocking everyone in the household. She claims to be Tenchi’s daughter, leading to a series of tense and emotional moments. Ryoko, Yuko Mizutani, immediately feels threatened and confronts Mayuka, denying her paternity and threatening her with an energy sword. However, Mayuka fiercely defends herself, summoning a powerful [faux-Lighthawk Sword] and refusing to back down. It’s only Katsuhito who manages to intervene and de-escalate the situation. Later, Washu performs a DNA test, confirming that Mayuka indeed shares half her DNA with Tenchi, solidifying her as his biological daughter.
The household begins to grapple with the bizarre reality of Mayuka’s existence, with many suspecting she might come from the future. Unbeknownst to others, however, Yuzuha is secretly manipulating Mayuka for her own entertainment. Whenever the others become distracted, Yuzuha exerts control over Mayuka, prompting her to act in questionable ways. At one point, Mayuka attempts to take Tenchi away to Yuzuha’s underworld lair. However, Ryoko breaks the trance, rescuing her and bringing her back home. Meanwhile, Katsuhito finds Mayuka in the woods, and she again tries to lure Tenchi away, only to be thwarted.
In a desperate move, Yuzuha takes Mayuka back to the underworld, erasing her memories and holding Sasami hostage—an act that prompts Tenchi and Ryoko to venture into Yuzuha’s world to rescue them. Once there, Tenchi is warned that he cannot use his Juraian powers, giving Yuzuha a clear advantage. Mayuka, no longer herself, transforms into a monster after being manipulated and attacked Ryoko. Yet, hearing Sasami’s words—that everyone cares for her—Mayuka breaks free from Yuzuha's influence, attacking her in turn. Yuzuha kills Mayuka for her defiance, transforming into a giant dark creature in her grief and rage.
As the story reaches its climax, Ayeka appears with a branch from the Tree of Light, enabling Tenchi to harness his Juraian powers. Using this strength, he defeats Yuzuha and returns home with Mayuka’s remains—a red crystal. Washu successfully resurrects Mayuka, though she requests everyone’s consent before proceeding. Despite initial resistance from Ryoko, she ultimately accepts and agrees to help train Mayuka in her new life. The story concludes with a glimpse into the future: Mayuka's crystal is used to bring her back to life, and by the next Christmas, she has returned as an infant, ready to be raised by the Masaki family once again, symbolizing hope, family, and the enduring bonds between them all.
