I don't remember that part... do you know which chapter? or at least its range... i don't want to read all of it again :'p
We saw Hakari and Hahari kiss during the "pretend drinking party" that was Momoha's integration. It's in chapter 110: Hakari announces she's so sensitive that she can tell whether she's kissing her beloved without looking. She kisses her mom, says "Not this one," then turns and kisses Karane, declaring "Yes, this one."
That said, chapter 44, "I Want to Eat Your Beef Tongue," had Hahari french Hakari off screen, and then established that she was kissing baby Hakari rather a lot. So there you go.