Minato was sad. Just think about it. Your student who you trained and cared for turns to the dark side. Minato tried to teach him to be a good shinobi but Obito was still turned by Madara. I'm sure anyone would be sad and feel like a failure after that
Madara. If it wasn't for him poisoning Obito's mind he may have gone back to the village. But now he's going to die after being forced to Rinne Tensei Madara. Unless Obio somehow while in excruciating pain realizes Madara lied,used him,and saw Obito as nothing more then a pawn and Obito rips the...