Tomarin hails from an alien planet and crash-lands on Earth when her spaceship runs out of fuel. This accident brings her into contact with Marimo, a student from Kameido High School's tennis club. The pair swiftly become roommates and forge a close friendship.

Tomarin bursts with cheerfulness yet scares easily. Her arrival fuels humorous misunderstandings about Earthly life and human customs, further tangled by Marimo's own incorrect assumptions. Their interactions consistently spark comedic misunderstandings.