Yukinari Sasaki is an average high school boy who has gynophobia (fear of women.) His childhood friend is Kirie, and he is also friends with an alien named Miharu, who came from a planet called "Siren" that is inhabited only by women. Somehow, Yukinari is able to touch Miharu without breaking out into a sweat. The "happy" trio has adventures and stir up commotion together! Act 1: Yukinari Sasaki is a high school student. He has female-allergy and female-phobia that were caused by girls who had been bullying him because of his short height. One day he accidentally opened the bathroom door where his next-door childhood female friend, Kirie Kojima, was taking bath. When she hit him out of her rage, Yukinari slipped into the bathtub and hit his head on the bottom. Then, he found himself in the different world called Siren, whose male population is less than 10 per cent. He met a girl, Miharu, there. Somehow he doesn't get an allergic reaction to her. While running away from those Siren women chasing Yukinari, both of them came to the original world for Yukinari by accident. Act 2: After she came to his world, Yukinari found out that Miharu had an extraordinary appetite.
When he left her home to go to school after telling her stay home quietly, Miharu become so hungry and couldn't help thinking about the bread sold at school store that Yukinari told her earlier. Thus, she snuck out of his house and came to his school to get the bread. Because she looked different from other students, she got all the attention there. After all the hassle, she ended up eating the lunch box made for Yukinari by Kirie because the bread at school store was sold out. Act 3: Yukinari and Kirie took out Miharu for her welcome trip to a cheap hot spring inn. At the hot spring, they encountered a ghost girl, who died and is haunting the place because of her regret that she couldn't catch the peeping tom who caused her death. In spite of their weaknesses for ghost and girls, Kirie and Yukinari helped the ghost girl by letting her take over Kirie's body and letting her catch Yukinari in her arms. Thanks to their help, the ghost girl could free her soul from this world. Act 4: For Miharu, it's the first St. Valentine's Day experience in this world.
Because Fukuyama snatched Miharu's handmade chocolate from Yukinari, Yukinari had to fight against many male students over the chocolate. At the end Yukinari got back Miharu's handmade chocolate for him to his hand. At the same time, he found out that Fukuyama had the male-allergy just like his female-allergy. Act 5: Fukuyama's sister, Risa, believes in fortune telling. Due to the words of her favorite fortuneteller, Madam Mabanya, Risa determined that Yukinari is the Man of Her Destiny. After their first accidental encounter, Risa started stalking Yukinari aggressively. She even used weird magic to catch Yukinari. Act 6: Because his mother left home to take care of his dad who collapsed on his business trip, Yukinari was left alone at home with Miharu. Yukinari told Miharu that he wanted to get over his female-phobia/allergy, so Miharu tried to support him even when Risa came over and harassed him. But Miharu couldn't help interrupting them when Risa tries to poison Yukinari with salt, which Yukinari told Miharu could be a poison to one's body earlier. Side story: This side story is an erotic parody of "Momotarou," one of old Japanese tales.
Momotarou (Kirie) was born from a huge peach. She went ogre hunting to save the village where grandpa (Yukinari) and granny (Miharu) lived. The Color Ogre (Fukuyama), the boss of ogres was having good time with those girls from the village. Although the old couple(Yukinari and Miharu) said that these girls were kidnapped, in fact those girls were there on their own will. Still Momotarou (Kirie) couldn't stand the lecherous lifestyle that the Color Ogre(Fukuyama) had, so she beat him up anyway.