The Main Villain of Tenchi in Tokyo
Yugi was a Juraian mutant who summoned a bunch of demons to be her playmates. Unfortunately, their fun accidentally ravaged the planet and fearing for Jurai's survival, the Juraian Empress destroyed Yugi's demon playmates and the young mutant winded up being sealed in a stone tomb. For the next 3,500 years, the tomb drifted through space before landing in Japan on Earth and being buried. An earthquake wrecked the tomb freeing Yugi as she sought to make her own world out of Earth.
While appearing as a little girl, Yugi is chronologically over 3,500 years due to the time she was kept sealed. She has blonde hair and purple eyes, normally wearing a red and black striped headdress with large spiked armor hovering around her.
While originally being a cheerful young girl, Yugi's mind became warped from the years she had been sealed and desires to create a place where she would be free to use her powers. In spite of being able to create human and demon familiars with her power, the mutant girl is internally lonely and would come to seek friendship with Sasami as she learned more about the girl throughout the series.
Yugi plotted to drive Tenchi and the girls apart as they each held the crystal pieces to a sword that was the only power that threatened her plans. She created Sakuya to drive Tenchi's attention away from the girls and wreck their bond while creating minions to preoccupy Tenchi's group or wreck havoc.
Meeting with Sasami in the middle of the series, Yugi's plans changed as she created a clone to interact with and play with the girl while keeping her away from the attack her true body made on the Masaki shrine. However using a portion of her power to sustain the clone prevented Yugi from being capable of winning the battle against the other girls. As Yugi's plans near completion, she attempted to have Sasami come with her. But scared of what Yugi had going on, Sasami rejected Yugi's request and the mutant teleported away in anger. She later has Matori kidnap Sasami and trap her in a large crystal as Yugi freezes time on Earth. Fortunately for Tenchi and the girls, the crystals to the sword prevent them from being affected by the time freeze. Rejected once again by Sasami to have their own world, an enraged Yugi decides to wipe out all existence on Earth. Tenchi and the girls are once again protected from Yugi's power thanks to Ayeka's force field.
Tenchi heads into Yugi's inner sanctum to confront the girl armed with the now fully-formed crystal sword. Yugi attempts to trap Tenchi in a world of dreams only for Sakuya's consciousness to snap him back into reality. Once in Yugi's inner chamber, the scared girl attempts to stop Tenchi by hurling attacks at him which he is able to overcome. Following a slap that sends everything back to normal, Tenchi tells Yugi that she could have come to the Masaki household if she feared loneliness. Following these events, Yugi places herself into a sleep stasis so she can learn to better control her power. Ryoko hypothesizes that with Sakuya being Yugi's shadow that Yugi would grow up to resemble Sakuya when she is physically older.
Yugi has the power to manipulate reality to such a degree that she is capable of creating human and demon familiars, freezing time, altering the terrain around her, creating copies of herself and trapping her foes in illusions within their minds. In battle, she is capable of flight, firing off energy blasts, teleporting and creating barriers to guard her from harm.