Hifumi has the best chara design and is really super cute, but she suffers from a lack of background and portrayal as we barely know or are shown anything about her except her cuteness.
Aoba is a pretty nice heroine, although quite vanilla, it is pleasant to see her gradually winning confidence.
But best girl title will go to Kou she is really likable and has a great interaction with Rin (best yuri ship!). From a professional point of view, her portrayal is quite realistic and interesting: she is someone who is very demanding toward herself but also rest of the team. Despite genuinely caring a lot about her subordinates, her lack of communication skill would cause huge dissensions in the team.
Unsurprisingly she still lack trust i herself and fear to manage a project once more.
She truly is the one with the most complete portrayal.
It's incredibly hard to choose since almost all of them are super cute, but I'll go with Yun. Her Kansai accent is absolutely adorable, I can't hear enough of it! Every time she speaks my heart melts. Plus, her loli features are nice!!
Hifumi is lovely too.
Umiko is really, really cute in her own way imo. I like the way she enthusiastically tries to make people she likes join her for some airsofting xD
umm. I will go best main character between aoba and ko? aoba. Best girl is ko, although they are the main somehow the ship is rin and ko. but still has moments with aoba. idk but my most adorable is probably Hifumi. she's cute. but lack of screen time and convo