Segawa Yuta is a freshman of a university. He lost his parents when he was small and was raised by his sister Yuri. Yuta has been living alone since Yuri got married to a middle aged man when Yuta was a junior high student.  One day, Yuri visited Yuta's apartment and asked him to take care of her three daughters while Yuri and her husband were on a trip. He unwillingly accepted the job but the plane Yuri took went missing. In order to prevent the daughters from being adopted separately by relatives, Yuta decided to take in all three girls.  A life of a strange family in a tiny apartment begins.

The story is based around 11-year-old Saga Bergman, a young girl in a small German town called Muhlenberg (based on real town of Rothenburg ob der Tauber). Saga lives with her grandmother Regina and works in a coffee shop when not in school. Saga is extremely structured and plans her life down to the minute. One day, she notices a tiny creature in a fluffy outfit that appears to be starving. She offers it a waffle, which helps revive the tiny creature. Saga learns that this tiny creature is Sugar, an apprentice season fairy. Sugar explains that season fairies alter the weather by playing a magical musical instrument, and her specialty is snow, which she creates by playing the piccolo. Sugar is joined by two more apprentice season fairies, Salt, an outgoing male fairy who plays the trumpet to make the sun shine more brightly, and Pepper, a quiet and caring female fairy who plays the harp to make the wind blow.