Yuuri

ユーリ

Yuri is a mysterious swordsman from an ancient past.

In his past, Yuri won a holy battle after he became one with the Sword of Light, but at the cost of his humanity. He has remained in the World of Avalon since then.

After meeting Kamiyama Touma in Avalon and having witnessed his resolve, Yuri departs from Avalon and enters the real world. Having stayed in Avalon for a very long time, Yuri is curious about everything the modern world has to offer.

Yuri joins Touma and Sudo Mei on their quest to stop the Megiddo and uncover the true nature of the Sword of Logos.

Yuri uses the Sacred Blade SaikouDriver to transform into the sword-like figure Kamen Rider Saikou.

Kamen Rider Saikou

仮面ライダー最光

Stunt actor: Arakawa Makoto

Transforms with Wonder Ride Books set into the Sacred Blade SaikouDriver before releasing the blade from the Driver.
Despite being known as the Swordsman of Light, Saikou appears in the form of a sword. He is also known as the Sword of Light.
Saikou is based on the Gold-tree and Silver-tree fairy tale. His element is Saikou (最光) or greatest light.

Kin No Buki Gin No Buki

金の武器銀の武器

Who is the shining sword? Saikou Chapter One. The blade shining gold and silver. Saikou!
First appearance: Ep 16

Height 121.0cm	Weight 23.2kg
Thurst/Slash Force 50.3t	Top speed About 300,000km (Almost the speed of light)

Kin No Buki Gin No Buki Wonder Ride Book is set into the SaikouDriver to transform.
Attacks enemies autonomously while in his sword-like form. Can also be wielded by other Riders, particularly by Kamen Rider Saber.
Spawns the Saikou Shadow to wield him in battle.

Saikou's default form.
Motif: Gold-tree and Silver-tree / Sword / Light
Finisher(s) via SaikouDriver:

Saikou Luminescence - Flashes a warm, bright light.

TV Asahi site

Saikou Shadow

最光シャドー

Who is this? Saikou Chapter Two. The shade born from the light. Shadow!
First appearance: Ep 17

Height 195.3cm	Weight 51.3kg
Punch power 9.5t	Kick power 18.8t
Jump power 19.5m	100m Dash 4.4s

A shadow summoned by Saikou to wield him in battle.
This shadow can attack the enemy at any angle by shifting to different positions.
The shadow can also extend itself while attacking.

TV Asahi site