Cosmic Princess Kaguya!

Iroha Sakayori, a high school student living independently from her family after her father's death, struggles to maintain a tight schedule of school, tuition and part-time work while also spending time in the virtual world of Tsukuyomi. On her way home one night, she encounters a glowing utility pole with a baby inside. Reluctantly taking her in, the baby rapidly grows up into a young girl over the span of a few days. The girl, claiming to be from the Moon, is named Kaguya after the Japanese folktale. Dejected by the "depressing" ending of the folktale, Kaguya aims for a "happy" ending with Iroha.

As Iroha's daily life begins to be disrupted by Kaguya, much to her annoyance, she introduces her to Tsukuyomi and its virtual administrator AI, Yachiyo Runami. Together with Kaguya's virtual pet InuDOGE, Kaguya and Iroha sign up for the Yachiyo Cup, a streamer tournament where the winners get to perform a live show with Yachiyo. Kaguya quickly becomes a popular streamer with Iroha's help, inadvertently placing them in the crosshairs of Black OnyX, the top streamer group led by Akira Mikado. After the group challenges the pair to a competition in KASSEN, a territory battle game in Tsukuyomi, Kaguya learns that Akira is Iroha's estranged brother.

Despite Yachiyo's assistance, Black OnyX wins the KASSEN match, but the outpouring of support from fans allows Kaguya and Iroha to win the Yachiyo Cup instead, securing their live show with Yachiyo as well as reconciliation with Akira, who agrees to co-sign a new apartment for the pair. The live show is successful, but after the performance, Tsukuyomi is invaded by mysterious beings, revealed to have come from the moon to bring Kaguya home. Although repelled by Yachiyo, the beings promise to come back by the next full moon, a fact that troubles Iroha, who is now unwilling to part with Kaguya.

On the day of Kaguya's impending departure, as she performs a graduation concert in Tsukuyomi, Iroha attempts to fight the lunar forces with the help of Black OnyX and her friends, but are ultimately unable to stop her from being taken by them. Returning back to her normal life but unwilling to accept Kaguya's absence, Iroha completes a song she and her father had never finished and plays it. After she does so, she reaches a revelation and logs back into Tsukuyomi, where Yachiyo confirms that she is a future version of Kaguya.

Having been motivated to return back to Earth by Iroha's song, Kaguya had attempted to travel back in time to reunite with her, but her ship had collided with an asteroid, sending her back 8,000 years into the past. Unable to leave her damaged ship, InuDOGE (who later became Yachiyo's companion Fushi) served as her communicator, interacting with people over the ages until the creation of Tsukuyomi, where she was uploaded into a virtual avatar.

Determined to bring Kaguya back into the real world, Iroha scraps her plans of becoming a law student and works on creating an android body for Yachiyo to upload her digital consciousness into. After ten years, she succeeds: they can finally be together and continue performing, this time both in real life and Tsukuyomi.