TENTATIVE... well, from day one, they were already deceiving and hiding things from each other, only they both believed it was to protect the other. Isa found out from Ventus that he doesn't have a heart, and made Ven promise not to tell Lea; likewise, Lea found the same thing out from Riku and asked Riku not to spill it, either. So they both knew there was something wrong with them, and after the Lion's game they were feeling shakier with feelings than usual, but it wasn't until after Kiriko's game (when Isa got the memory of what Nobodies are and Lea got the memory of killing Zexion) that things started to come out. Right now I think they're closer as a result, but there's a lot of shared pain between them and they're not really sure how to cope with that.

Roxas's top 5 most important people in Aather!