Yup only ash can still be sane after going through all that I mean he got a whole life of strict training, then despair of not being able to use magic, almost trained himself to death only to receive despair, got abandoned by his family, got deceived by his tutor the first person on whom he puts his trust in and let's not forget the 100 times dosage of a drug that can actually drive a person to madness from pain at normal dosages and ash survived 100 times that pain cause he was numb to pain but demon lord isn't.