Kouichi Uehara is a fourth grade student living in the suburb of Tokyo. One day, he picks up a large stone which turns out to be a fossil of a baby Kappa who has been sleeping underground for the past 300 years, and names it Coo. They become good friends and Coo starts living with Kouichi's family. However, Coo has a hard time adjusting to life among humans and misses his kind.

Japari Park is an untamed paradise where many humanoid animals, known as Friends, live their everyday lives in all corners of the natural environmental park. One lazy afternoon in the savannah area, the energetic Serval encounters a peculiar new Friend. Curious, she swiftly takes down the Friend, named Kaban, to try and discover what species she is. To Serval's disappointment, not even Kaban herself knows the answer. The two become friends and set out on a grand adventure through the many habitats, landmarks, and attractions of Japari Park. Their destination is the park library, where they hope to shed some light on Kaban’s identity. Along the way, they meet many other Friends, looking into their lives and helping them out. However, they soon begin to uncover the sinister reality behind the park and their own existence.

Tokiko Mima, nicknamed Key, is a 17-year-old girl living in the Japanese countryside who, despite her human-like appearance, is a robot. When Key's grandfather Dr. Murao Mima passes away, he leaves her a dying message, telling her that she can become a real girl if she is able to make thirty thousand friends. Thus, Key moves from the quiet Mamio Valley to the busy streets of Tokyo, where she soon runs into her childhood friend Sakura Kuriyagawa. Key quickly becomes enamored with idol singer Miho Utsuse and wonders if becoming a singer will allow her to make the amount of friends needed for her to become human. But Miho carries a ominous secret: she is connected to Jinsaku Ajou, an old rival of Dr. Mima trying to make new a breakthrough in robotic weaponry. As Key works to become a real girl, Ajou sets a dangerous plan into action, and it turns out there's much more to Key than meets the eye.

Ever since the death of his father, the burden of supporting the family has fallen upon Tanjirou Kamado's shoulders. Though living impoverished on a remote mountain, the Kamado family are able to enjoy a relatively peaceful and happy life. One day, Tanjirou decides to go down to the local village to make a little money selling charcoal. On his way back, night falls, forcing Tanjirou to take shelter in the house of a strange man, who warns him of the existence of flesh-eating demons that lurk in the woods at night. When he finally arrives back home the next day, he is met with a horrifying sight—his whole family has been slaughtered. Worse still, the sole survivor is his sister Nezuko, who has been turned into a bloodthirsty demon. Consumed by rage and hatred, Tanjirou swears to avenge his family and stay by his only remaining sibling. Alongside the mysterious group calling themselves the Demon Slayer Corps, Tanjirou will do whatever it takes to slay the demons and protect the remnants of his beloved sister's humanity.