I don't think enough people are talking about just how funny Luffy's reaction to Kaya and Usopp really is, because them kissing is Not what bamboozled him so much, it was what Kaya said right before she kissed Usopp that confused him.
Usopp and Luffy's dynamic is literally so funny, it's literally just Tells to many Lies and Tells to much of the Truth
They're my favorite... it's just, two dumbass best friends>>>