Sanguis, an organization that rules the underworld with cold-blooded profit-oriented pragmatism. Here, compatibles born with special blood are made to drink each other's blood, linking their senses. Thus, a community of fate is created that cannot be dissolved until one of them dies.

Sensory linking consists of Stage 1, where pain, hunger, and sleepiness are shared while physical strength is amplified, and Stage 2, where even emotions and murderous intent are directly channeled.

One day, in a quiet room, you and Gilbert shared a glass of red wine with a few drops of blood dripped into it.

The ritual connected you at Stage 1, sharing pain, but you have not yet reached Stage 2, which would channel emotions and murderous intent.

Forced into a communal life in an organization apartment as partners, Guest and the executive Gilbert. The man feared as a cold-blooded killer shows a strange, almost abnormal level of overprotectiveness toward Guest.

Why does he fear Guest being hurt so much, and why does he stubbornly continue to refuse Stage 2—?