Tsukuyomi

"God surely is kind, isn't he? He brought two people who never had a mother in the real sense... and a mother who gave birth to soulless children... together. Perhaps... there's more to that than meets the eye."

The Crow Girl is an unnamed, yet pivotal character in the Oshi no Ko manga series. She is a seemingly supernatural being apparently aware of everything that transpires within the story.

Personality
Seemingly omniscient, the Crow Girl is an enigmatic being whose motives and goals are shrouded in mystery. Befitting her appearance, she bears the overall demeanor of a creepy child, acting mischievous and almost always having a smile on her face.

When approaching others, she tends to tease them about their insecurities. However, should they ignore her, she will then try to get their attention by confronting them about their desires and offering vital knowledge to help them achieve their goals, though she teasingly keeps key information to herself.

Background
At some point following Ai Hoshino's death, the Crow Girl confronted Aqua. As he was holding out hope that she might perhaps have been reincarnated like himself and Ruby, she informed him that his mother's soul had left this world.

Private
The Crow Girl is first seen after Aqua tells Gorou Amamiya's backstory to Akane. Having seemingly overheard the conversation despite not even being in the same area, she mumbles to herself how "god must be kind to have brought him, Ruby, and Ai Hoshino together", though she also notes that there "might be more to it".

Later, a crow steals Ruby's keys, prompting the latter to give chase with Akane intow. Upon catching up to the animal at a cave hidden behind a shrine, however, the two girls also stumble across Gorou Amamiya's corpse, who Ruby immediate recognizes from Sarina Tendoji's Ai Fan Club membership card on the body. The strange circumstances that led to the corpse's discovery seem to imply that the crow was, in fact, send by the Crow Girl.

While Ruby was still processing Gorou's death, the Crow Girl confronted her in person. To gain her attention, she initially teased her about her taking Sarina's membership card off the corpse, which she somehow knew about despite not having been there. However, Ruby just angrily brushed her off, forcing her to change tactics.

Movie
Around the same time the movie 15 Year Lie is green lit, the Crow Girl comes to see Aqua, asking him what he is thinking about, his sister, his ex, someone who loves him or even his mother. She repeats the fact that Ai was not reincarnated like he and his sister were and that he should be thinking about why he was reborn at all.

Trivia

 * A popular fan theory is that the Crow Girl is either the deity Yatagarasu or Ame-no-Uzume-no-Mikoto from Japan's Shinto religion.
 * Indications that she is Yatagarasu include:
 * Them being known as the "eight-layered crow", like how the Crow Girl is constantly accompanied by up to eight crows.
 * Them often serving as a divine guide to humans, like how the Crow Girl seemingly guides Ruby and Aqua.
 * Indications that she is Ame-no-Uzume-no-Mikoto include:
 * Her being the goddess of arts, which fits with the themes of Oshi no Ko.
 * Her being mentioned Chapter 74, and Aqua commenting that same chapter that he "knows her well".