Did Natsume confess to Mikan

Yes he did. Telepathically with her telling him first in chapter 134 of the manga and then out loud in chapter 144 when they meet up on the balcony of where Mikan is being held. There is a heartwarming and touching scene where Natsume tells her to confess to him out loud. She does while calling him and idiot and moron, then he confesses to her and they share a kiss <3.