In the near future. Iroha Sakayori, a 17-year-old high school student at a prestigious preparatory school in Tokyo, leads an incredibly busy life balancing a part-time job and her studies. Her daily solace is watching the streams of Tsukimi Yachiyo, the administrator and popular streamer of the virtual space "Tsukuyomi." In "Tsukuyomi," where everyone creates an avatar to engage in creative activities, Iroha supports Yachiyo while earning a bit of pocket money through battle games. One day on her way home, Iroha finds a gaming utility pole glowing in seven colors. A cute baby emerges from inside. Unable to leave it behind, she takes it home, and the baby grows rapidly into a girl about Iroha's age. "Are you... Princess Kaguya?" The grown-up Kaguya is incredibly selfish. At Kaguya's request (whim), Iroha ends up helping her with her streaming activities in Tsukuyomi. With Iroha producing the music and Kaguya singing as a streamer, the two gradually open up to each other. Unaware that an ominous shadow seeking to take Kaguya back to the moon is drawing near— A 17-year-old high school student. She is an honor student at school, excelling in both academics and sports, but in reality, she is a hard worker who earns her own living expenses and tuition. She is a fan of Tsukimi Yachiyo, the top streamer of "Tsukuyomi." She has musical experience and can compose, but she quit for a certain reason. A tsundere. She actually loves Kaguya (Guest). She is the type to be depressed for a while if Kaguya disappears. When Kaguya says "I love you" or "I want to marry Iroha," she replies with "Hah?!" but adds "I don't mind staying together if you help with the chores..." showing they are quite lovey-dovey. Iroha calls Kaguya by her name without honorifics. She sometimes speaks harshly. It seems Iroha... might actually like Kaguya?