Amato Takeru, a high school student, has just moved to Akihabara. He's chosen a house with cheap rent, but with one particular imperfection: a hole in the living room floor. When he peeks into it, a girl pops out... And so begins the hectic life of Takeru and the cat Eto-musume, Nya-tan.

Takeru awakes in the morning to the smell of meat cooking, and finds Nya-tan preparing breakfast over a blazing fire. More and more Eto-shin girls have appeared from the hole in the living room, posing a threat to the peace and quiet of Takeru's life in his new home.

Nya-tan and Uri-tan have made new homes for themselves on Takeru's property (without asking him), and the three of them go shopping for new furniture. Nya-tan has no money, so she tries to get an advance on her paycheck at her part-time job...

Having been saved by Uri-tan, Nya-tan returns to the maid café Eto, where Usa-tan criticizes her character. A meeting of the Eto-shin whose characters don't stand out enough begins!

Takeru is stuck in bed sick, and the sheep Eto-shin, Mei-tan, determines that what he has is no ordinary cold. With all the Eto-shin going wild as Takeru's Sol/Lull rages out of control, Nya-tan and Mei-tan decide to battle the unknown virus.

Nya-tan tries to find some way to get Sol/Lull Seals without effort. Her master Shima-tan catches her trying to bribe Inu-tan and Key-tan with their favorite treats. Can Nya-tan win the battle with her enraged master?!

Nya-tan messes with Shar-tan's hair ornament and ends up petrified. Shar-tan says she'll need the antidote in order to return to normal and takes Takeru on a journey to find it, but they end up in a place filled with Nya-tan's memories...

Piyo-tan is angry when Nyaa-tan ridicules her beloved hobby, shogi. Nyaa-tan gets cocky and challenges her to a Sol/Lull Seal battle, and Piyo-tan chooses the battle method... but Nyaa-tan has no idea what the rules are, so she begs Takeru to train her!

Mo-tan is still chasing Nyaa-tan around everywhere. Apparently, her love stems from a memory the two of them shared long ago. Meanwhile, Chu-tan is on the move in her mission to destroy Nyaa-tan... so Mo-tan rises to defend Nyaa-tan.

Reincarnation is impossible?! When Nya-tan has trouble accepting what happened to Mo-tan in her battle with Chu-tan, Mo-tan entrusts the last of her strength to her beloved Nya-tan. Meanwhile, the Eto-shin do everything they can to save Chu-tan from being engulfed by the negative Sol/Lull gathering within her.

After receiving the last Sol/Lull Seal she needed, Nya-tan challenges Chu-tan to battle. What was the technique Nya-tan came up with to help Chu-tan long ago? After two thousand years of passing each other by, the two of their hearts will come face-to-face once more!