I knew it was obito, too obvious from a few chapters ago.
Even duh, there's a lot of options.
1: Dead people don't grow, yet, we don't even know if he was dead...they just let him die there, under the rocks, when he could have even awakened mangekyou and susanoo'd rocks or kamui'd his own ass/rock.
2: Its not obito, but someone using his body or face, or whatever's going on.
3: It is Obito, got friendzoned and his feeling of kakashi being superior to him he cannot handle it (Yet its funny, he's even more powerful lmao..). Supporting this one a lot, since a flash back means it has something to do important with Obito or yet its Obito. He seems to be the opposite of Naruto (Instead of Sasuke, which isn't, he's just gay and dumb as fuck).
Obito was always the true bad guy, watch all be plan of Obito, Sasuke get mindfcked, mad at him and teamwork with Naruto to defeat nigga.
EDIT: Forgot another option, watch it be Zetsu's body and obito's head.