The parents of the protagonists were childhood friends and promised to marry their children in the future.

This wish comes true, and the Bin family has a daughter and the Taira family has a son. A few years later, the wife of the Taira family dies, and the second wife joins the Taira family.
The second wife also gave birth to a son, but the second wife was not pleased with the first wife's son and poisoned him, nearly blinding him and forcing him to abandon him in a cave.
At that time, the God appears to her in a dream, and the daughter decides to follow the oracle and rescue the young lord abandoned in the cave.