Yukinari Sasaki suffers from quite the rare (and pathetic) disease of being overcome with measles when touched by a female. This is apparently due to his general dislike of females following his childhood because of excessive abuse at their hands. However, one day, a girl randomly appears in his bathtub out of nowhere. She is from the planet Seiren, (which orbits earth) her name is Miharu and other than popping up from a portal in a bathtub she is quite peculiar. Firstly, she eats like a horse, and secondly, she is the only female that does not induce Yukinari's girl-allergies. As Miharu adapts to life on the planet Earth, Yukinari becomes the one responsible for her welfare, and several new troubles arrive every day...