Hm !!! I'm not sure what angle you want me to talk about lol so I'll just . share my thoughts about the netflix show in general and then the main characters, and I hope you won't be too disappointed...

overall I really really liked akuma kun for how stylish it looks, the charming cast of characters, and the choice to mix detective show and monster of the week formula together. but man the pacing was weiiiird and like . it's something i will gladly forgive if we get a season 2, because the series was written with a sequel in mind definitely and it would feel really unfair to the audience if we never get it u_u in a way, it didn't really bother to introduce newcomers to established (1989) akuma kun lore, which is a Choice I can understand ; it assumes you already know so it can focus on all the new things it's trying to bring to the table. the thing is, new akuma kun introduces a Lot Of Ideas, leaving the watcher expecting it to be developed later, but because it's stuck in Netflix Hell its future is uncertain and it just leaves me anxious personally lol. so again : if all those ideas get to be fleshed out in the future i would be super excited about it, if not well... i'll be upset the show wasn't more carefully paced and, too ambitious in its ideas.

really the center of the show is ichiro and sansei's relationship isn't it? ichiro looks like he doesn't feel (but plot twist.. he does!), while sansei looks like he feels too much - it's a classic dynamic in detective shows, but with the peculiar supernatural aspect of akuma kun, I like the idea of a half demon teaching a human character how to be human ; not in the biological sense but in the, moral? sense. humane rather than human, i guess.

if you look at sansei he's the most human of the cast really, he feels, he loves, he hates, he experiences all the good and the bad. his family is so normal and well adjusted it's comical given his father's identity. they share meals together, they enjoy beers, they work, they live their life. it's all very Mundane to sansei of course, but it's the complete opposite of ichiro's side of the family. and I like that it's through sansei that ichiro gets to enjoy the Ordinariness of human existence, mostly through the senses and well, food. not just food, but the food that you make for someone else, and the food that someone else made for you, be it pancakes or ramen... thanks to sansei, ichiro gets a taste of normality, and he learns to cherish it. it's a simple story arc, but it's charmingly executed I think...
(those feelings of "love", towards shingo, sansei, and everything life has to offer, i do believe he had them in him since the beginning, he just never learned to rationalize them before the end of the show... which is why i prefaced this mentioning the pace, which makes the show almost feel like a Prologue to ichiro's character in a way...)

The flipside is that, while that normality is so important to ichiro, it weights heavily on Sansei, who is constantly made aware of his "half" status. it makes him self conscious of course, as a character whose identity, whose name is directly tied to the legacy he has to uphold, as a Mephisto AND as akuma kun's sidekick. had it not been for said legacy, would he have bothered to even make friends with ichiro? would he even have looked his way...? I.. don't think so LOL. but sansei is duty-bound so even if Ichiro is difficult to work with, even if he depends on him to unlock his powers, even if said powers are weaker than his dad, he will continue to work hard and do his best...

I remember thinking initially that Ichiro and Sansei's relationship feel very inequal in that Sansei is weak and depends on Ichiro to unlock his powers AND crack cases. technically ichiro should be the brain and sansei the brawn (. or well. magical dps . you get me.) but sansei isn't even that efficient at his role... but well, throughout the series it becomes clear that sansei IS important to ichiro's stability and happiness. My wish would be in a sequel for sansei to be more or less explicitely made aware of this fact, and for him to gain confidence in himself... it would even that unfairness in their relationship quite a bit imo. Ichiro owes soooooooo much to Sansei, I want to hit him behind the head and tell him to give him a little kiss and thank you already!!

And as for an eventual future development for the both of them...
because Ichiro is often shown pushing Shingo away and rejecting his role as "akuma kun", I would really like the show to go deeper into the fact that ichiro and sansei are their own person before being "akuma kun and his sidekick". acknowledging that they were put into these roles whether they like it or not and how they deal with being duty-bound/Literally The Chosen One. (it's interesting how shingo and nisei's bond came more naturally ; shingo had a Predisposition to the akuma kun stuff by being an occult and demon nerd, and nisei got to be his tsundere little oresama self before warming up little by little to shingo.... while ichiro and sansei's relationship felt much more abrupt and awkward.)
ichiro is able to set boundaries (maybe a bit too much LOL) with shingo and assert himself as his Own Person, no matter how much of a weirdo he is ; as such, I would LOVE for Sansei this time to learn this from Ichiro - for him to put some distance with his duty as akuma kun's sidekick, step out of his father's shadow, and find out who he is beyond Mephisto Third Generation, you know?!

ahh, they have such a great relationship these twos, really...
obviously i LOVE ichiro/strophaia a lot too, but because your ask was pretty vague I chose to rant about what I feel is the Driving Force Of The Plot lol.
it's interesting the series plays with an initially established human/demon dichotomy, but then you find out sansei and ichiro are not quite fitting on either side... and actually, shingo and nisei neither - shingo, human, so devoted to his role he seems mostly cut off from everyone else in the mienai gakkou, nisei, demon, having completely adapted to human society... and in the end, the big bad is someone, something we're not even quite sure what it is, not a human (ew!) not a demon, maybe not even an angel? blood not red nor blue but black...?! that line between humans and demons is blurred more and more with every episode until in the end there's no line at all, just characters trying to live no matter who and what they are, against the character who is neither human nor demon trying to take away their life :).... it's really great!

the "thing" that wants to destroy everything for everyone else, tries to mold a blank canvas of a person into his tool for his greater schemes... but said blank canvas escapes from his grasp, and becomes what the "thing" wanted to destroy in the first place .. it's wonderful... !! the story can't end here..... i need more of sansei, ichiro and strophaia.......... !!!

^ i can feel myself going on another rant about ichiro and strophaia so i'll stop here. sorry i word vomited i'm too lazy to proofread myself LMAOOO

akuma kun is great......!!!!! .. has the potential to be great if they write more....... !!!!!!! i won't forgive them if they don't...!