Since there's no summary, I'll just give a little blip on what this is about. Basically, there's this island with torii (those arches in front of temples) that serve as doorways to "Ryuuguu" or the world of the gods. The door only opens once every seven years and they mainly focus on worshiping the ocean god when it does. Well, this little girl, Yura, finds a boy washed ashore on the day that the doors to the Ryuuguu are open. She takes him home with her and there's no reports of a missing kid and he doesn't seem to have been kidnapped or anything. Her parents want to send him to an orphanage, but she demands that he stay with her as her "little brother." Well, seven years pass and the time for the doors to Ryuuguu approaches quickly. Yura is recruited as the mika who will dance for the ocean god, symbolizing her getting married to him. Nao, the boy Yura found, may just be a gift from the sea after all.

There's more, but I'm sure it's cliche enough for you to figure it out. It's really cute and the art is beautiful. Highly recommended for a oneshot. I loved it! <3