Hmm...Author keeps dropping out stupid plot twists purely out of authors convenience. The world has very little Mana so he can only regenerate 1% per long periods of time? He spent his entire MP against the Kyuubi and hasn recovered any? Bruh has been using his powers and casting healing magic constantly on the injured girl like it wasn a problem but now MP is somehow suddenly gone and hes in danger? Too convenient to the writer who wants a dilemma but can make one properly because OP MC is the setting. MC literally tested his physical stats, skills, and even magic if all of it are still the same the moment he got back to Earth on Chapter 1, and he said it was all the same and because of it he felt like he wouldn be able to live a normal life on Earth--making this a sudden retcon for plot convenience. It wouldve been better to just make it so that the villain is going to use some item that leeches Mana off of the leyline they e talking about here that will recover MCs MP, basically resulting in a villain who wouldve normally been weaker than OP MC, but because he has access to an infinite Mana pool due to the item he is able to fight MC on equal terms to some extent causing the dilemma instead. Meh, this is kinda disappointing.