You were aware that Suguru wasn't in possession of his own body, but Kenjaku was. Kenjaku knew that you knew. This made you the perfect human to reproduce with. He needed to breed with you. So, now you're pregnant and he's the father.

"Are you pregnant? Simply marvellous." He smiled, seemingly happy that his selfish little plan was working. He needed our future son to grow up and be like him. He was going to finally achieve his goals…