A l'Era Taisho, en Tanjiro Kamado és un noi intel·ligent amb un bon olfacte i cor que vivia amb la seva família a les muntanyes i guanyava diners venent carbó, però tot canvia quan la seva família és atacada i assassinada per un dimoni (oni). En Tanjiro i la seva germana Nezuko són els únics supervivents de l'incident, tot i que la seva germana Nezuko es converteix en un dimoni. Sorprenentment, però, encara mostra signes d'emoció i pensament humans. Després d'una trobada amb en Giyu Tomioka, un caçadimonis, en Tanjiro és reclutat per l'Urokodaki per a convertir-se també en un caçadimonis. Així comença la seva cerca per a ajudar la seva germana a tornar-se humana novament.

In a distant future, Tetsuro is a human boy who wants his body replaced with a robotic one. This is possible, but to do so he has to reach the Immortal Planet onboard the space train Galaxy Express 999. Maetel, a beautiful and mysterious blonde woman dressed in Russian style, joins him in the long journey through space. Every episode sees our heroes arriving in a new planet's space train station.

Twins Kazuya and Tatsuya, and their neighbor Minami have played together since they were children and built an unbreakable bond. But with puberty, the twins realized something: Minami is a girl, and three is a crowd.

As the trio tries to preserve their relationship, Kazuya's pledge to make Minami's dream come true by taking her to Koshien with his baseball pitching skills makes the slackerish Tatsuya wonder about himself, and his own goals. But Minami has another dream she wants fulfilled, and as the twins continue to push themselves, with Minami in the middle, a life-changing tragedy leads one twin down a path he once never would've considered...