In the near future, 17-year-old high school student Iroha Sakayori is attending a prestigious school in Tokyo and leads to a hectic life, juggling her part-time job and studies. She finds daily relaxation by watching the streams of Yachiyo Runami, the administrator and super-popular live streamer of the online virtual space "Tsukuyomi." One day, on her way home, Iroha finds a pole shining with rainbow lights. Out of it emerges an adorable baby. She takes the baby home, and it quickly grows into a girl named Kaguya, about Iroha's age. At Kaguya's request, Iroha decides to help with her live-streaming activities on Tsukuyomi. As Iroha creates music as a producer and Kaguya sings as a live streamer, the two gradually grow closer. They have no idea that an ominous shadow is looming that will take Kaguya back to the moon.