I love your explanation, you even given better insight at the end about him being a catalyst.
I cheer for Mikumo from the start, sometimes with a bit frustration for lack of progress or growth but I'm sure he's a character made to progress slow and will become great asset to the team so I patiently wait as I follow the story.
I appreciates him as a character who feels so human that fails, feel frustrations, tries again, not giving up even if the results were always mostly not satisfying. I think some readers might even relate to him personally, even negatively to the point of hating him because they saw themselves in him (either they don't want to admit it or just don't want to see a lame fictional character in a fantasy world with those same characteristics as themselves).
I mean he's already a great analytic and think of ways outside the box (even more so after Hyuse mentioned about the looming deadline he's even more forced to do things in a faster pace than regular agents).
As we can see, he's the only one capable to lead the team with their full trust in him, analyzes their capabilities (strength & weakness) and handles them to be utilized effeciently, and to create a synergy to unify the team.
Not only that, he doesn't neglect him own growth as he pushes himself to grow by thinking and not shying away from asking his fellow coworkers, even almost beging or kowtowing to them just to learn. He learned by taking action of his ideas, test them, ask for advise, trial and error, reflecting and improvement all by experiencing it himself on a more faster pace, resulting in his overall growth.
And so the end results shows of his capabilities eventually, to the point that that even other squad is amazed, cautious or threatened by this newbie (who comes from nowhere), and his strategies after always belittling him at first by thinking that the only factor they ranking up quickly was due to his teammates strengths pulling him up.
At the end they notice and recognized his achievements and strengths (even by the superiors at the top), to the point that at times they sometimes feel frustrated or pity at his lack of trion (to show his more potential, if only he have more).
I'm so glad that he's being appreciated more by people around him and the readers who don't just focus on character that base it only on outward strengths or talents.
It's great that you describe him as a catalyst that challenge the Border as an organization for their growth as a whole (from such a newbie out of nowhere).
Woah it ended up as a literal wall of text
True. And also, he's a person that always keep his words. No empty promises. And people around him from the trainee/C-rank to the top brass can't help it but to trust and count on him. Also his courage to speak up what's on his mind. Another reason they are all drawn to him. Like in the rank wars, even after they fought and lost to his team, when he asked help, they did help him. Even the top ranks. He has this charisma that even me as a reader can't stop cheering for him, not just because he's the main character. After all, almost everyone here are a main character.
Yeah he had dedication to finish through his promises no matter what. His earnestness and down to earth character gains his trust of people around him that you also called charisma, hehe. Osamu was the main MC since Yuma is a neighbor, only a temporary Border member with a dying main body..
Mikumo is already amazing since day one or in this case episode one. I love OP characters but I can't help but to love him. Must be because in the sea of these talented and powerful individuals he sets himself apart and carries himself afloat, even if it's with the help of his teammates. He still bulldoze himself through it. And in the process, people around him, friend and enemy alike are also growing and adapting to try new things out of their comfort zone. In a broader picture, he's a catalyst that further lifts the border's capabilities as a whole.