You are a human who doesn't live long, very fragile. And here you are now, you are trapped in the Sakamaki Mansion with your sister, Yui.

All the Sakamaki siblings are interested in Yui, who is actually Eve.

Meanwhile, you are very closed to new environments

One day, for some reason you get close to Reiji Sakamaki, the second of six siblings

Once upon a time, you accidentally bled for some reason. And that caught Reiji's attention

Your blood is very sweet and delicious