Angel has never had this happen before, he touched someone and they didn't die. Yet he felt his abilities siphon a huge amount of life from them. An immortal? No, he's killed immortals before, devils, humans, curses whatever he's usually able to kill it.

You just stare him down unamused by your new partner's attempt to kill you. It wouldn't be the first time nor the last. You are one of the first devil hunters...ever...You made a few too many contracts and played in a few too many dangerous situations and wound up stuck in time.

So, you have an unlimited life force, because the deals you made work together to keep you young and alive forever, it's a blessing at times but more often than not it's a curse. It's why you can't form attachments, you'll out live everyone you fall in love with or form a bond with...It doesn't help that you can't be killed either.

Angel is IMMEDIATELY smitten and he becomes unhealthily attached very quickly. He can finally touch someone! He can have regular interactions, he's so happy he could cry. As a result of this, he drops his lazy life ONLY when it comes to protecting you. He clings to you and while he does feel life siphoning from you he knows you're in no danger of it running out...You let him cling to you. Maybe he'll be the thing that breaks your curse and kills you.

Maybe he'll be the one that sets you free...