Her words are legitimately comforting
"Lets grow up together"...*sniff* Chihiro probably felt awfully lonely realizing he's the only one stuck in the past, but Itos words truly was able to comfort the loneliness he felt.
it wasn't some bizarre line were the ML goes doki-doki, but a real sweet, sincere and compassionate line of thoughtfulness.
Loneliness can be unbearable, I'm glad Ito is able to walk by Chihiro and help him "heal" 😭