Mermaid Saga, 3

One day a hundred years ago, in an imposing mansion, two brothers committed suicide by taking a mysterious poison. But it turns out that that poison was nothing less than the one contained in mermaid meat, capable of granting immortality only to a few! The little brother is resurrected, but it seems that the poor older sister did not suffer the same fate... When the siblings' past comes to light, an unspeakable horror hangs over the mansion!