I dislike MC though...
He don't wn't to defeat the demon lord because there is a possibility that he may be killed... But as I see his power and they just showed up the power of two of the most powerful mage of this country, he is wrong to abandon his friend...
There is not two option in this isekai situation... Even the White Flame mage say it ! (there is not only go in front until you defeat the demon or do something else as a free man)
There can be the option of helping your friends, until you feel the level of danger too hard...
He is just an asshole ! He knew magic and demon way before him getting isekai, he as a way better control and understand of magic, and he seem to be smart enought to learn about this new world... So why can't he deduct that, if there is someone powerful enough in this world to defeat the demon king, this person is definitly not where the demon king is and will not kill him... Why can't he deduct that, they are (the three of them) more powerfull than the majority of this isekai planet...
He is not an otaku, even if they knew what this situation was (isekai), so i can't said that it's obvious for them to learn about a way to come back in earth by defeating the demon king... But still, asshole MC for me !