Yes, maybe that's why Masami knows so well what's going on - she probably watched Masaki for a while already, and maybe realized Nino's feelings during that time. :-)
I think Jun really wanted to find closure, and he knows his sister likes Sho, so he wanted to give him the chance to talk everything out. He is still feeling hurt, but now he can finally move on for real. And we all know that Satoshi is waiting for him and ready to heal his wounds :D

Thanks so much for your lovely comment! I'm so happy you are following this story <3