A squid-like creature called a Happian ventures beyond his home planet, aiming to spread happiness throughout the universe. When he arrives on Earth, however, he nearly falls into the hands of the locals. Luckily, a solemn girl named Shizuka Kuze saves him and provides him with sustenance, affectionately dubbing him Takopii. In exchange for her kindness, Takopii dedicates himself to bringing joy to Shizuka's life.
But the undertaking proves difficult, as Shizuka suffers from bullying, lacks a father figure, and has no present mother. Oblivious to the weight of these issues, Takopii notes that Shizuka's only happiness comes from her pet dog, Chappy. This observation only fuels his determination to bring a smile to Shizuka's face.
As he tries to spread happiness, Takopii unintentionally causes unexpected problems. Nonetheless, he persists, utilizing his knowledge of human nature and his unique tentacles to accomplish his goal of sharing joy.