If I were in your shoes, I don't know that no matter how hard I tried, I wouldn't be able to keep myself from being attached. The long and the short of it is, if you know you're going to keep him if you get attached.. just decide to keep him and enjoy the fact that he loves you. Even if you don't get attached, he already seems to be forming a bond. You may end up keeping him for his sake.
Hehe, if you took our household.. my sister would complain and yell that she can't keep him, and then opt that we just can't get rid of him. Me, I'd be like, welp, yeah yeah, we'll look for a home (to appease her) and the whole time, I'd have absolutely no intention of finding a new home for him. I personally just can't stand to get rid of them once they're with me. Of course, sis is wise to this, and has in the past said.. hmm, why is it that I know you're not really planning on getting rid of that cat...? :whistle: Of course, if she didn't moderate my behavior, I'd probably have at least 10 kitties..some people have better control than I do.
It seems like it would be torment to both of you at this point, to rehome him.
If you absolutely have to, it's understandable, but if you don't.. keep him and enjoy it.
I'd just sit back and enjoy the good deed you've done, and know that Neko knows what you've done for him too. That's the best gift (besides saving him), forming the bond with him.