"he wants the best for his love"...is he buying the best dog food?? I'd rather have my life extended than come back as a DOG! - I don't want to take shits in public. This is humiliating!
I mean I don’t wanna be a dog either but the MC chose to die and meet his demon again in all his next lives. Nicholas (I think that’s what the demon’s name was) was right in the sense that his lover would suffer a lot more as an immortal (the same way the human who was forced to live a lot longer is suffering). Although it’s painful for Nicholas to the point he’d rather die with him but he still chose to wait because he’d rather suffer than let his lover suffer.
Honestly I was wondering why Nicholas didn't ask the other demon to extent his boyfriend's life. The answer he gave was so true and shows that no matter what he wants the best for his love