[Hijikata has heard stranger stories in his life (not many, but even so), and he trusts Sagi to not just troll him for no reason, so he's totally buying it! He won't let him off the hook regarding the state of his soul so easily, though.]

Why does he live inside of you? How did that happen? Did he possess you..?

[Right now he suspects that Sagi basically allowed a ghost to share his body with him out of the goodness of his heart, and that's just not right. Despite Hijikata's lack of experience with the possession-related aspects of death magic the gears in his heads are already turning to find a possible solution for the situation.]

Anyway, we don't know what happens if you agree to this blood contract. Will only your soul get bound to Dionysos since it's originally your body? Or Marno's as well, since it's his body too now?