Paradise Lost and God Speed Love are movies that serves as an alternative ending/timeline for their respective series and are both written by Toshiki Inoue. They also feature a dystopian/post-apocalyptic world.

Both Paradise Lost and Missing Ace are movies that serves as an alternative ending for their respective shows. They are also written by Toshiki Inoue.

Both are movies of a Heisei Kamen Rider show that follow an alternative ending to the series. They are also written by Toshiki Inoue.

Both are alternative endings for their respective Kamen Rider shows featuring the darker tone of the early Heisei series.

Shin and The First/The Next are retellings of the the original Kamen Rider TV show/manga, featuring a darker and more realistic setting. The protagonists were transformed into a superhuman being against their will after became a test subject of human experiments.

Both shows have a police/detective theme where the protagonists solve cases involving crimes committed by the villains of their respective series.

Both Kamen Rider series feature an amnesiac Rider who is 'adopted' by the family of the heroine (which has powers). There are also four main Riders.

Both Kamen Rider Ryuki and Ex-Aid have several Riders fighting each other through competition and betrayal while facing monsters in their respective stories (Mirror Monsters / Bugsters). Both also have a secondary Rider with a knight motif.

Both shows share a dual of protagonists (Shotaro and Philip/Eiji and Ankh) who work together to fight the monsters of their respective series (Gopants/Greeeds). The transformation gimmick of both main Riders uses different kinds of combinations which allow them to activate various forms.

Both Kamen Rider Agito and Ryuki share similarities in the dark tone and the mystery that surround the plot of the series.