Kasugano Haruka and his sister Sora have lost both their parents in an accident, and with them all their support. They decide to move out of the city to the rural town where they once spent summers with their late grandfather. At first everything seems familiar and peaceful, but changes come as Haruka starts to remember things from his youth.

* Based on an adult visual novel by UNiSONSHIFT. What if, when watching the stars outside the window... What if, when writing in your secret diary at the end if the day... ...A mysterious light suddenly falls from the sky... Tsuwabuki Masaharu, or Haru as his friends like to call him, is your normal middle school student. Now in his second year, his friends push him to speak with his classmates whom he has yet to speak to, but this was still difficult for Haru due to his clumsy nature. One afternoon, his life met with a 180° turn during a strange encounter in the hallways of Hoshigaoka School. During that fateful encounter, he accidentally drank a magical potion which makes him transform into a stuffed animal sheep during the night! Haru later learns that in order to return to his original self, he needs to collect "star droplets" that fall from the sky. However, being that his innards are now made of cotton, he will need the help of a "special person." Little did he know that the special person was someone from his class. Living a double life between his day-self and his sheep form "Yuki-chan," page one of his story, her story, and the story of nanatsuiro drops begins...

Many years have passed since humanity was driven to the brink of extinction by the sudden emergence of the unknown life forms Gadoll. Those humans that survived now dwell in a 3000m-high mobile fortress Deca-dence built to protect themselves from the Gadoll threat. Denizens of Deca-dence fall into two categories: Gears, warriors who fight the Gadoll daily, and Tankers, those without the skills to fight. One day, Natsume, a Tanker girl who dreams of becoming a Gear meets surly Kaburagi, an armor repairman of Deca-dence. This chance meeting between the seemingly two opposites, the girl with a positive attitude who never gives up on her dreams and the realist who has given up on his, will eventually shake the future course of this world.

Morphed into a raccoon beastman, Michiru seeks refuge, and answers, with the aid of wolf beastman Shirou inside the special zone of Anima-City.