I wonder how long it'll take for Akamatsu to have Negi re-appear. I mean, as stated before, it's obvious that there's just no way he's dead. Not only because of the effects of Magia Erebea but the fact his death was never confirmed, just assumed because he disappeared apparentely. I believe it was mentioned that when he first 'died' (if not sometime before) in the final battle with the fates, actually I believe it was when he was still stone and he saw his father, raken, eva and what not, that if he chose to returned that he'd be choosing to become a monster/not human anymore or whatever. Come to think of it, it was near the end of the manga (before the festival where everyone tried to find out who he liked) he had a battle with Asuna and eva where Raken and the others were talking about the 'price' he and asuna had paid to save the world, with setsuna.
Which makes me wonder if Akamatsu is just pulling another act like when it was made to look like Nagi was dead. Which makes me even more curious as to what happened to him. Another shady group? I'm just that Touta will uncover it all in UQ Holder! It's probably engraved in the main plot, you never know.