Since ancient times, there has been a book being in charge of all existence on Earth. The book was engraved with all sorts of myths, stories, living things, sources of science and technology... When humankind evolved and civilization was developed, the knowledge and powers were written in there.

The book was protected by the "Holy Sword" and the "Selected Swordsman", keeping the world in balance. However, thousands of years ago, people who tried to rob the book appeared,. The books were scattered around the world and disappeared. The battle was secretly going on...

Time flows to the present age ―― Novelist Kamiyama Touma (Shuichiro Naito) had a recurrent dream: in a different space, a swordsman fights a fierce battle with a monster in a book, and a "mysterious girl" seeks help... Every time he dreams about it, Kamiyama Touma is caught in the feeling that he "forgets something important", but he doesn't know what it is or who the girl is. It seems that everyday life is so easy to collapse... The dream always happens without warning.

Suddenly, a strange phenomenon occurs where part of the city disappears. Important family members, friends, lovers disappear in front of each other eyes in a mess.

On the other hand, part of the disappeared city appears in a mysterious world. "Where are you?" "What happened?" "How can I get back?"... The desperate people wonder. Touma and Mei Sudo (Asuka Kawazu), the editor-in-chief, are suddenly involved in this phenomenon. Surprisingly, the other world is very similar to the dream that Kamiyama Touma often has, and like the dream, mysterious monsters invade and begin to destroy the city.

"I will definitely bring the city back to its original world!" Suddenly, a flaming sword appears as if responding to Kamiyama Touma's thoughts. As soon as he picked up the sword, he wears the power of the dragon, becoming "The Swordsman of Fire".

Tokyo Ska Paradise Orchestra akan membawakan lagu Opening dan Ending dari Kamen Rider Saber.
Kamen Rider Saber adalah Kamen Rider pertama di era Reiwa yang memiliki Ending song. Zero-One sebelumnya tidak memiliki Ending Song.
Di franchise ini , terakhir kali Kamen Rider memiliki Ending Song ialah saat serial Kamen Rider Hibiki (2005) dengan lagu berjudul Shōnen Yo yang dibawakan oleh Akira Fuse