I think the genre of this manga is action, ecchi, and supernatural.
The main girl has multiple personalities, and every time she changes her personality, her body changes, too.
I remember in the first chapter, as she was being chased by some people, she ended up transforming (or like I said, changed her personality) and killed them.
Well, that's all that I can remember. Please help me find this manga.
This sounds a lot like Gun x Clover. It is an action and ecchi manga, according to mangaupdates, and I think the female protagonist's power can be considered supernatural.
This is a page from the first chapter, showing Futaba - the 2nd personality of the female protagonist. The girl has multiple personalities (7 in total), and whenever she changes her personality, her body features (and even her outfit) also change to match the personality.
This is another page from the first chapter, showing Mitsuba - the 3rd personality of the girl. As you can see, her hair turns white as the 3rd personality takes control, and she becomes violent and capable of killing people. This is right after the scene where Futaba got caught by mercenary and was about to be defiled, when the 3rd personality Mitsuba surfaced to protect herself and killed off all the small fries.
