I understand your mindset, but from my perspective, a character has to be more than skilled, determined or good-looking for me to like them or even be invested. Their personality, attitude and/or quality of writing has to be above or equal to these criteria. In Bitchuru's case, they weren't.
I wanted to like Mitsuru, I really did, but out of all the S.E.E.S members, I found her the least dynamic and the least likeable.
For most of the game, she barely has any real interactions with her other dormmates - most of the time, she just gives them orders and asks them for favors. Often, it seems like they matter to her more as assets rather than as classmates or even comrades. Her friendship with Akihiko (who, to her credit, I never cared much for either) isn't adequately fleshed out, and practically nothing is known about her standing with Shinjiro, and his with hers. Given how they fought alongside her before, you'd think her relationships with them would receive a little more attention.
On top of that, she's proven herself time and again to be an idiotic, manipulative hypocrite. She had to have known that Yukari's father was somehow involved in Koetsu's experiments on the Shadows, and yet she deliberately kept her in the dark. Whether Yukari already knew or not was irrelevant; for all Mitsuru knew, she didn't. Finally, she and Akihiko brought Ken and Shinjiro into the fight when they knew all too well that the latter inadvertently killed the former's mother; did they really think that Ken would seek retribution if he found out, or even already knew? As far as I'm concerned, they're as much responsible for Shinjiro's death as Takaya is; I'm amazed that so few people call them out on this.
Like I said, I wanted to like her. But in the end, in spite of her development later on, I couldn't help but despise her.
Anyway, I don't want to start some big debate, and I'm not trying to change anyone's mind.