Yuri is the physical embodiment of the Kougouken Saikou and a protagonist in Kamen Rider Saber. He inserts the Kin no Buki Gin no Buki Wonder Ride Book into his sword form to transform into Kamen Rider Saikou.
He is portrayed by Tomohiro Ichikawa.
2000 years ago, Yuri was an old friend of Tassel who was present in the Wonder World with him. He took part in the War of the Wonder World that erupted when the Megid attempted to steal the Book of Ancients, and wielded both the Kougouken Saikou and Ankokuken Kurayami. To prevent either of the swords for being used for evil, Yuri gave up the Ankokuken Kurayami and merged himself with the Kougouken Saikou before having himself and the King of Arthur Wonder Ride Book sealed away in Avalon.
When Touma Kamiyama ventured into Avalon to regain his powers, he encountered Yuri. Yuri congratulated Touma on entering Avalon and gave him a test to see if he was worthy of King of Arthur's power. After Touma passed the test, Yuri told Touma they would meet again after he unlocked King of Arthur's true power.
When the Sword of Logos Riders attacked Touma to take his Wonder Ride Books, Yuri intervened in the fight to defend Touma and fight off the Riders. Yuri then explained that he chose to side with Touma in his quest to uncover the traitor in Sword of Logos and that the Sword of Logos had become corrupted from within.
Yuri would later meet with Tassel to asking for help in regaining his physical form. Tassel gave the Wonder World Story of Kougouken Saikou Wonder Ride Book to Yuri, who used it in the Kougouken Saikou to create the X Swordman Wonder Ride Book.
Kamen Rider X
Kamen Rider Amazon
Kamen Rider Stronger
Kamen Rider Super-1
Kamen Rider ZX
Kamen Rider Black/RX
Kamen Rider Kuuga
Kamen Rider Ryuki