[Mikan opens and closes her mouth a couple of times, hesitating. How does she tells him that this happened in the course of like, 2 years??

Well, maybe she doesn't have to. It's probably better for him to think like this. Besides, she's too distracted by the fact that he just headpatted her. She flinches as though expecting something harsher, and freezes when she realizes the touch is gentle instead.

Her head lifts some as she stares at him with wide eyes that immediately begin to fill with tears. She wipes at them furiously and sniffles] Th-th-thank you...! I, umm... I don't... M-mind it so much here, even if it's a little weird. It's so much more peaceful! Th-there's no fighting or people being k-killed in the streets, or riots or anything. A-and everyone I've met has been so nice too, i-including you...!