A nice and sweet slice-of-life, with a touch of fantasy-adventure. It is too short to expect a detailed story or deep characters, but it doesn't matter. We see just enough to understand the main characters and their relationship, and they feel as real as random boys.
The visuals are far better than average series, and even better than many featured films. I especially liked the attention to lights and backgrounds.
Not a masterpiece, not at all original, but beautiful and sincere.