Yearning to get along with others and not be disliked, first-year high school student Hiiragi finds himself unable to say no whenever someone requests something of him. One summer day, while unsuccessfully carrying out yet another request, he encounters an oni girl named Tsumugi, who has come to the human world to search for her mother. She does whatever she pleases and is the complete opposite of Hiiragi. Snow mysteriously begins to fall... and their adventure begins.