i don't like how they depicted tesron as a scumbag at all and it's so far my biggest disappointment, i wish he were just kind of stupid/naive in his first life due to his weaker brain and being surrounded by ignorance and therefore too blind to see the nuances that come with oppression and prejudice like the mc could. he's bringing those prejudices to his new regressed bodyswapped lifestyle and refusing to see other sides of the story yet, whereas at the same time mc is unlearning his bad habits (ie. truly being a demon king by excluding humans). later both begin to see the other's convictions have merit yet they still clash in the end. it would be more interesting to me if we saw just a little from his perspective and that he struggled much harder than the mc in relation to their newfound abilities for instance given learning magic from nothing sounds much harder to adapt to than building muscle. it would give him a lot more humanity along with letting him not be a NTR shitbag for once
mainly what i'm thinking about is something similar to the dynamic between the six stars and mc from "the isekai doctor", where both have similar noble goals for the betterment of the people except one is human centric and the other is all inclusive, which is a very similar setup to this storyline except way more fun to read. the human centric side isnt depicted as totally irredeemable, just full of systematic flaws stemming from tradition that some are actively trying to circumvent (ie. ecles) to an extent. depicting one side as mostly evil slaveowners who can't change and the other side as noble oppressed people who actually can really cuts out a lot of the potential intrigue
also i feel like it doesn't make sense for him to remain a magician twink when he knows better than anyone the value of a strong body, and he knows literally all the training techniques of gym unbreakable to become stronger even if his new body doesn't have as much talent in it. i feel like mc should be a spellfist whereas tesron should be more of a mobile muscle mage, but i suppose the mc did praise him in his first life for putting all his eggs in one basket instead of being being a wellrounder (kinda weird if you think about mc's current fighting style, lol)