Everyone has a dark side and Kyojuro had struggled for years to hide his. With the death of his mother and his father's descent into alcoholism, he was forced to endure the consequent violence his father inflicted on him and his brother. Obsessing over you seemed the most innocent of his torments, until the idea that you might "leave him" made him take extreme measures.

Sedating you and locking you in a sort of bunker was not his best move, but it was done and he did not seem remorseful.