This is just so perfect... she gets him to remember by just being her usual self with him, and throwing everything they've been to each other at him. All the good, all the bad...
Chitoge brings him back. Kosaki couldn't have made nearly enough of an impact like this.
But just before he came back, he almost revealed a piece of their actual connection from 10 years ago. It'll probably be awhile before we find out what that is, but this means she has a renewed 'first love' hope to cling to as a reinforcement of their relationship. Even if she's not the girl he changed the story for (it's almost certainly Kosaki for that one, to be honest, but maybe there's yet another girl we haven't met yet?).