I don’t play video games, but fortunately an astute reader of this blog recently alerted me to the game Little Nightmares as a possible GU story, and from what I’ve read, it seems to fit. Set in a labyrinthine place below (if not actually underground), female adversary for younger girl, adversary’s minions, no parents, final showdown with adversary, and even the rare ending where the girl becomes an adversary-type creature herself. The only thing it seems to be missing are companions. The following plot description is abridged from Wikipedia, and contains spoilers:

A nine-year-old hungry girl named Six is trapped in The Maw – a surreal resort catering to the whims of sick and powerful creatures. After waking up in the lower depths of the Maw, Six decides to escape the harsh confines, having regular moments of insatiable hunger. Whilst ascending, she soon becomes stalked by the long-armed blind Janitor of the Maw….After evading the Janitor by cutting off his arms via a door, Six follows the conveyor belt upward, to a large kitchen operated by the grotesque Twin Chefs….After managing to evade them, she manages to find a way out, but finds that the entire Maw is covered by a large ocean.

Six observes a boat ferrying large and obese suited Guests, who lumber to the Japanese-style dining area of the Maw, overseen by the Lady, the supposed leader of the Maw….Six makes her way further upwards, entering the Lady’s quarters. The Lady lives very lavishly in an elegant home, with many broken mirrors throughout the rooms. Chased by the Lady, who displays magical powers, Six finds a mirror that she uses against the Lady in a battle. Defeating her, Six approaches the Lady and eats her; in which she gains the Lady’s powers.

Going downstairs to the dining area, Six walks along the tables with strange black particles swirling around her. As the Guests notice her presence, they attempt to eat her, but suddenly convulse and die as Six walks on. Six approaches a large door with an eye encrusted upon it, revealing a large staircase leading to the outside world. 

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