Kamen Rider Ryuki (2002)

All over the city, innocent people are being mysteriously abducted, never to be seen again. During his investigations of these incidents, Shinji Kido – an intern at the online news service ORE Journal – discovers one of the Advent Card decks at an apartment where every reflective surface has been covered by newspaper. He is soon sucked into the Mirror World, discovering the terrifying truth behind the disappearances: people are literally being pulled through mirrors by the monsters of the Mirror World so that they may feed. He is about to be killed by a powerful dragon named Dragredder when he is saved by Kamen Rider Knight: Ren Akiyama. Ren seeks to win the Rider War at all costs. He works with a young woman named Yui Kanzaki, who seeks her missing brother: the master of the Rider War, Shiro Kanzaki. Seeing Ren's strength, Shinji enters the Rider War not for the prize, but so that he may protect innocent people from the threat of the Mirror World, and stop the senseless fighting between the Kamen Riders. With Dragredder as his Contract Monster, he becomes Kamen Rider Ryuki.