This is the story of Puniru the slime and Kotarou, a middle school student, until they cease being friends...

Kotarou Kawaii is a second-year middle school boy. When he was in elementary school, a slime he created came to life, and for the past seven years, he has been spending time with the slime named Puniru as his "friend." However, there is one problem for Kotarou...

Over the seven years, both have grown significantly, and Puniru has transformed into an incredibly beautiful girl!

Besides her beautiful appearance, Puniru freely transforms into various cute forms as a slime, causing Kotarou to be both excited and bewildered by her carefree behavior every time.

Will Puniru and Kotarou be able to continue spending time together as "friends" despite these challenging days ahead?