(from ebookjapan):

One day, a man goes hunting. On the way, he sees a wild cow stuck in a muddy swamp, and with desperate effort, he saves it. Some years later, a mysterious boy appears in the man's village, saying that he has come to look for his father. The boy says that his father is the man who once saved the wildebeest.

The boy takes the man to his mother's place, and the man is led to a wild cow...