Kuroe Akaishi is an introverted, quiet, and seemingly normal high school girl. Though accustomed to being alone, her dreary days begin to change when she meets Arata Minami, a bright and handsome boy in her class. Despite his popular status, he is kind enough to reach out to an outcast like her; soon, Kuroe finds her heart begins to pound around him.

It keeps pounding and pounding and pounding until Kuroe transforms into a monstrous kaijuu! She has a certain affliction: as her embarrassment grows, so do the monstrous appendages from her body; and when it hits a peak, she unleashes the full extent of her transformation.

At the same time, beauty meets the kaijuu, and Japan faces off against the looming threat of the mysterious monster. Can Minami accept her feelings, or will he too be frightened off by her colossal form? Depending on his decision, the world may experience the full devastation of a girl's heart-pumping, youthful love.