@Loksel
This kiss was him retroactively and reactively reciprocating Ibusuki's love, so if Eve was a normal Zombie she would have disappeared.
It seems to me that he's living out the memory as a firsthand experience. When he says "Even though I love Eve this much", I think he means Ibusuki. Not Eve, not little girl Eve, but present Ibusuki.
It's safe to say that he won't forget the promise now, unless Ebino is waiting around with a bunch of softballs to lob at his head. ???