
SPOILERS:
1. You'll hate Yua even more.
2. The story is already so deep, the manga doesn't do it much justice.
3. The manga also doesn't do Aresh's feelings justice. And it actually tells about how Aresh rapidly falls in love with Kondo and how quickly Aresh comes to terms with his own feelings. The manga just makes him look like he's shouting, angry and brooding all the time. But he's just a whore for Kondo's attention.
4. The manga doesn't cover enough, Ik this is irrelevant to some, but the vice captain of the 3rd knights, Aresh's cousin, isn't jealous of Aresh at all! He's actually quite fond of him and enjoys doing all the work that Aresh never pays attention to. He enjoys being the silent backbone of the knights due his cousin's neglect. Lol. The manga made it look like he was scared that Aresh may become competent, which he is scared of, but not for the reasons the manga shows.
5. Did I mention that you'll hate that selfish little brat Yua even more?
6. Ps. Aresh confesses to Kondo FIRST!!!
7. In the next chapter Kondo is about to get the shit beaten out of him poor baby.
8. But the prime minister finds him and Aresh has seggs to save him. (It's hot and consensual)
9. The prime minister is kind of a good guy. He has Aresh's interest at heart.
10. Aresh and Kondo will eventually be having seggs all the time for that barrier thing he brought up.
11. You'll fkn hate Yua
12. Aresh is baby

WAIT so yea thats what I was confused about! I didn't really understand how Aresh fell in love with the MC, like was it love at first sight? A gradual occurence, like was he attracted to our MC'S high competence and seggsy reasoning?? Pls elaborate since the manga makes it seem like Aresh is hulking out 24/7 lol

It wasn't love at first sight.
Mostly, ML was bewildered at how little MC took care of himself and his obsession with work. It's sort of like interest born from frustration before continuous exposure turns it into caring then into love (for ML).
MC has such a lack of self-perseverance that ML couldn't leave him alone and took it upon himself to take care of MC since no one else (including MC) would. But then his possessive/obsessive side got the better of him the more he took care of MC and then MC is one of the few who criticizes his way of doing things as head of the 3rd Knights Order. He just ends up thinking about MC a lot.
It was a gradual accumulation of them interacting together and their constant thinking of each other that made them realize that they've ended up developing feelings for each other without them noticing when it began. MC takes longer to come to terms with it (bc he's been in serious relationships--with women--in the past and isn't sure if he wants to take the same steps with ML, who'd be the first guy he's been with).
Luckily, once ML notices his own feelings, he's the proactive type and just confesses. That and MC doesn't have that much of a hang up on sexuality--his concerns lay more with work and efficiency, which the ML utilizes to his advantage.

Yua gets (much) better but it's mostly shown in the 2nd volume and only partly seen the beginnings of at the end of this first volume.

It isn't love at first sight like the other person mentioned. But it was interest at first sight! Something the manga failed to capture, made him look extremely broody! In the novel, in Aresh's POV, Aresh even thought that Kondo was way more inconvenienced than Yua coming to this world. I think he first fell in love right after they had seggs. He even gave deep thought about Kondo's behavior right after. He attempted to make an excuse for himself as to why he would care for such an otherworlder, but he fell short and came to terms with the fact that it was "another reason". He even asked his cousin for advice!
In the other chapters, when they finally started having seggs constantly, Kondo thought that the intimacy was unnecessary and didn't want to fall in love with Aresh. He said something along the lines like that to Aresh. But Aresh didn't gaf . He knew that Kondo didn't love him yet, but he still wanted to take full advantage of the situation so they could have seggs all the time. Honestly, they both knew they were taking advantage of eachother for different reasons. Aresh for seggs and bc he loved Kondo and Kondo for Aresh's magical ability and position.
Aresh even improved on his work to try and impress Kondo!! So cute.
Damn, double homicide.
I CAN'T STOP WHEEZING OMG