Because the lips would be a way for the poison to enter her body which would hurt her, basically she has so somehow ingest it for it to be harmful, not harmful on the outside of the body.
I can’t fully remember but I think he (regularly) consumed some kind of poison to not go rampage or something,, and that poison is deadly to a normal human being. The poison is kinda a part of his blood so he can’t kiss her or he’ll transfer the poison over her.
You should re-read again, it explains why in some of the chapters.
No I understand why he can't-I meant more like why can he kiss everything but her lips?
Ahh I just thought it was like the poison in his blood and saliva was hazardous no matter where it touched. But that makes sense considering he'll kiss everywhere else lol
Because mouth is one of vulnerable entries acquiring poisons (sedative drugs to avoid Del's killing people and making him calm) and dels secretions such us sperm cells, saliva, blood, tears etc. is all contaminated by the poison (=・ω・=)
I don't understand how he can kiss other parts of her body but lips are a no no?? I mean they can at least like have a peck?