Will Seth rape her? No, will he kill her? Yes, but did that mean he would foolishly kill off his only source of knowledge on the soul fruit? No.
When Seth had said her death wouldn't be quick, he hadn't been joking, he planned to torture the woman tile she spilled everything she knew and then keep her a little bit longer to get some confirmation on her words before ending her.
"You said you'll let me go when I find what am looking for, but how do I know you won't stall my search or lock me up somewhere so I would remain with you for a long time or forever," Irene asked.
"Because other than when you're pleasing me, you'll be the one pushing our pace as I will accompany you on your search," Seth said.