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."

Tsukuyomi, real name unknown, is a pivotal character in the Oshi no Ko manga series. A seemingly supernatural being inhabiting the body of a little girl, she has an, as of yet, unexplained connection to Aqua and Ruby.

Appearance
Tsukuyomi has been described by Taishi Gotanda as a "creepy-looking child" reminicent of Aqua when he was younger. She has light hair and eyes that are always wipe open, causing her to give off a disturbing stare. In terms of attire, she dresses in a black and white child school uniform.

Personality
Seemingly omniscient, Tsukuyomi 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 being unfazed by threats whilst almost always having a smile on her face, with Taishi Gotanda even comparing her to a young Aqua.

When interacting with people, she tends to tease them about their insecurities. While partly a tactic to quickly get their attention, Tsukuyomi seems to be genuinely interested in others' thought processes, implying that she cannot directly read minds. However, should they ignore her, she will quickly change the topic to get their attention back, such as by confronting them about their desires and offering vital information to help them achieve their goals whilst teasingly keeping critical details to herself. Still, she does not appear to be malicious, merely giving her information and inquiring others to think on it.

Still, Tsukuyomi does have a more "human" side to her, taking pride in her supernatural status and getting angry once insulted. This, ironically, leaves her open to being manipulated herself through others exploiting her haughtiness. She has also shown to be stubborn, refusing to admit when she has been tricked.

Background
According to Tsukuyomi, her current body is not her own but a "vessel" given birth to by a mother, comparing her situation to Aqua and Ruby reincarnating as Ai Hoshino's children. She also adds that said mother is not a normal person either.

At some point following Ai Hoshino's death, Tsukuyomi 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
Tsukuyomi 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 in tow. 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 Tendouji'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 Tsukuyomi.

While Ruby was still processing Gorou's death, Tsukuyomi 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. She reveals to Ruby that there were two people behind Gorou and Ai's deaths, the stalker and a middle schooler, but does not disclose the identity of the latter, telling Ruby that it is her duty to find out.

Movie
Around the same time the movie 15 Year Lie is green lit, Tsukuyomi 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.

The Girl reappears to retell Ruby's past life and her relationship with her mother, Marina Tendouji. As she narrates, Ruby goes to the Tendouji home to find that Marina gave birth to two new children shortly after Sarina's death, leaving her devastated at the fact that her mother did not love her. After Aqua reveals to Ruby that he is Gorou's reincarnated self and helps her get back on her feet, Tsukuyomi observes from afar and says Aqua made a bad move.

One week before the filming of the movie, Aqua is once again visited by Tsukuyomi. Aqua asks the Girl about her parents, to which she answers that her mother, whom she considers not a "normal" parent, gave birth to her vessel, just like the twins. To her surprise, Aqua then asks her to play the child role in the movie. The Girl believes Aqua is joking and reminds him of her otherworldly power, but Aqua continues asking if she can act. Eventually, she agrees in irritation after Aqua tells her to make an apology if she cannot do it, and Aqua introduces her to Gotanda as a child actor.

Trivia

 * Tsukuyomi's name originate from the deity Tsukuyomi-no-Mikoto the goddess of the moon in Japanese mythology.
 * Coincidentally Tsukuyomi-no-Mikoto is a sibling of Amaterasu, the deity that Ruby once pretended to be back when she was a baby.
 * Prior to adapting Tsukuyomi as a stage name, a popular fan theory is that Tsukuyomi is either the deity Yatagarasu or Ame-no-Uzume-no-Mikoto from Japan's Shinto religion.
 * Yatagarasu is also known as the "eight-layered crow", like how Tsukuyomi is constantly accompanied by up to eight crows.
 * Yatagarasu is often serves as a divine guide to humans, like how Tsukuyomi seemingly guides Ruby and Aqua.
 * Ame-no-Uzume is the goddess of arts, which fits with the themes of Oshi no Ko.
 * Ame-no-Uzume was mentioned Chapter 74, with Aqua commenting that same chapter that he "knows her well".
 * Tsukuyomi's statement that Ai's children were "soulless" implies that she would have had a stillbirth if Gorou and Sarina were not reincarnated as her twin children.