Kanashimitsumugi, Aiutsushi.

The great tree at the center of the island was revered as a god.

Among the island's people, the god would choose one with a symbolic birthmark. That birthmark was the mark of sacrifice. He who bore it was desired by the god, and must be given to it as an offering. That was the custom of the island since time immemorial.

Zen was destined for sacrifice. Until then, he passed his days together with Hata. One day, Zen encountered a wandering merchant named Daito. In himself Zen found a forgotten light, an unknown wish: that he might escape his inescapable fate. And so, he began that futile pursuit.

[From DLsite English]