Theory that I'm fairly confident of: Komari became a vampire because while she was taking her last breaths, she inhaled the red mist emanating from Liberta when she went beast mode which I'm assuming was her blood vaporizing.
I suppose I like this manga. Their romance seems a bit too convenient and sudden and liberta feels a bit like a Mary Sue. I like the comedy though and i really like their fashion style. Liberta is a very classic lesbian from 2008