|This article is about a/an rider in Kamen Rider Decade.|
Ren Haguro is a former journalist of the Atashi Journal and Shinji Tatsumi's former best friend, mysteriously leaving the group three years ago without explanation. Ren has the ability to transform into Kamen Rider Knight and use the power of his Contract Monster, Darkwing. When Reiko is murdered, Ren enters the Trial to find the Rider who possesses the Time Vent Card. After defeating Scissors, Ren encounters Decade in a brief confrontation before Zolda intervenes. Later while forced to fight Shinji who accuses him of playing a part in Reiko's death, Decade's fight with Imperer stops theirs. Soon after, Decade battles Knight with the former being the superior fighter until Abyss intervenes. After defeating Odin, Ren acquires the Time Vent card at the cost of being too injured to use it himself.
- Height: 195 cm
- Weight: 95 kg
- Punching Power: 10 t (200 AP)
- Kicking Power: 15 t (300 AP)
- Maximum Jump Height: 40 m
- Maximum Running Speed: 100 m per 4.5 seconds
- Sight: 10 km
- Hearing: 25 km
Haguro can transform into Kamen Rider Knight's default form using his Advent Deck and V-Buckle upon forming a contract with Darkwing. His Visor, the Dark Visor, is a rapier that also functions as his personal weapon. In comparison to Ryuki, Knight has lower kicking power but higher jump height and running speed.
In addition to the Dark Visor, Knight can arm himself with the Wing Lancer (ウイングランサー Uingu Ransā), a lance derived from Darkwing's tail, by using his Sword Vent Advent Card. The remainder of Darkwing's body can be mounted on Knight's back, where its wings become a cape. This can be done by using either his Guard Vent or Final Vent. (However, Ren is often seen transforming into Knight with the cape already equipped). When using the Guard Vent card, the wings are in their original form and close around Knight to form the Wing Wall in order to protect him from attacks.
Using his Final Vent allows Knight to perform his finisher, the Hishouzan (飛翔斬 Hishōzan, lit, "Flying Slash"), which equips him the Wing Lancer and Darkwing's cape form if he does not already possess them. Knight then jumps into the air and performs a drop kick while holding the Wing Lancer downward, resulting in it being parallel to his legs. Finally, Knight's cape forms a drill around him before he strikes the enemy.
- Advent Deck - Transformation device and Advent Card holder
- V-Buckle - Transformation belt
- Advent Cards - Trinkets that enable a Rider to summon Contract Monsters, access equipment, and use special abilities
- Dark Visor - Knight's Visor that enables him to use Advent Cards
- Ride Shooter - Motorcycle used by any Rider to enter the Mirror World
- Main article: Darkwing