The series centers on the misadventures of 17-year-old Kana, a high school junior who spends her days hanging out with her besties, Mossan, Hijiri, and Pets. They live unremarkable lives, until the day a Mecha falls out of the sky, along with a strange woman named “Haruko.” Her plans for Kana and her friends involve the force known as “ATOMSK.” Kana will have to risk everything to decide whether or not to help… like she really has a choice!
Kana Koumoto, a cheerful 17-year-old, can often be a klutz and nosey; one day, while hanging out with her best friends, Pets, Mossan and Hijiri, they start making a rocket using empty soda bottles.
One morning, Kana and her besties witness Hijiri kissing a college student Toshio inside his car. Acting more mature than any of her classmates, Hijiri suggests Kana and her besties to do a photo shoot with Toshio.
Mossan is the most mature of all 4. With a passion of becoming a designer, she has been working outside of school. Upon discovering her working towards a fashion contest, Kana feels the urge to help her, which rubs her the wrong way.
The 4 girls come watch the basketball game that their Sasaki is a member of. Kana has been secretly in love with Sasaki, whom Haruko ends up making out with. This triggers Kana's NO to activate, but she notices that and runs away.
One hot summer day, the 4 girls and Haruko are playing in the pool. They notice that Pets is missing. Kana later hears from her classmate Aida that Pet's family is very rich and they are moving to Mars.