Due to the nature of her father's job, Seto Hinoka has transferred schools several times. When her friends from her first school ceased contact after her transfer, Hinoka resolved never to become close to anyone again.
Now in her seventh transfer school, she meets a strange and excitable boy named Morino Yuuki who seems eager to become friends with her. When it's time to choose a club, she decides to join the idle astronomy club, thinking she could continue living her life alone. But it seems like Yuuki is already in the club! What's more, the club is now expected to use teamwork to build a planetarium! What will happen to Hinoka's solitary life with this club, and a boy who shines like the brightest star, Sirius, on a cloudy day?