Plot

Kamen Rider Saber × Ghost is a TTFC-exclusive crossover special between Kamen Rider Saber and Kamen Rider Ghost. In the crossover, Takeru joins forces with Touma as they take on remnants of Danton's evil forces. The special features the debut of the Ghost Ijinroku Wonder Ride Book and Kamen Rider Saber Ghost Ijinroku.—Kamen Rider Wiki

Touma and Mei find a girl who is looking for her brother. When they try to talk to her, she is attacked by Desast and runs away. Why is Desast after her? Touma and Mei chase after Desast to learn more. Meanwhile, as he's looking for Kanon, Takeru finds survivors of Danton's experiments and vows he won't let them be sad like Chloe was. When he goes off to look for more survivors, he runs into Touma and Mei.—Kamen Rider Wiki

"Everyone, Bonne lecture. It's me, Tassel. There was once a young man who died and came back to life. On his path to resurrecting himself, he bonded with a variety of heroes and saved the world with many friends by his side. While on this corner, we have a young man who fights with books and sacred swords in order to protect the world. And now, these two tales fated to be entangled. I simply cannot contain my excitement!" --Tassel.—Kamen Rider Wiki