Natsu no Tomoshibi

One day a young boy arrived at this village, holding a letter in one hand and his sister's hand in the other.
They had no place left to go but the address written in the letter he was holding. Since they traveled with one-way tickets, there was no way back.
In the end, they were accepted as a part of the family living at the address written in the message, and started their new life in the village.
A village full of spirits and protected by gods summoned into mirrors...