|Yusuke Onodera is very assertive, guileless, and precocious. Yusuke supports the police in fighting the Grongi and has feelings for Detective Ai Yashiro, as he fights to see her smile. He was really hurt by Yashiro's death and was effected when he met a look-a-like of Yashiro in the Agiro World. When Yusuke first discovered the Arcle Belt, he was the first to be warned of Decade's existence as the 'devil' by Narutaki. Yusuke rarely engages in battle while journeying with Tsukasa. He does, however, act as an inspirational figure to the other Riders, as can be seen with his aiding of Wataru, as well as his actions in the other Riders' worlds. However during the Rider War, though his world is destroyed, Yusuke still exists due to his traveling of the Nine Worlds. Even though he is destroyed by Decade in The Last Story, he and his world are restored, allowing him to aid in reviving Decade and defeating the newly formed Super Shocker forever. Just like the original Kamen Rider Kuuga, Kuuga can change into various forms such as Mighty Form, Dragon Form, Pegasus Form, Titan Form, and Growing Form when defeated.
Yusuke has mostly used Mighty Form, transforming once into Titan Form while in the Amazon World and Dragon Form in the Decade World. In the Agito World, Yusuke dons the Kamen Rider G3-X suit for a while, believing he belonged in the Agito World as it was much like his own Kuuga World. During the visit to the Den-O World, Yusuke was possessed by Momotaros, who uses him as a body to transform into Kamen Rider Den-O Sword Form. Decade's Final Form Ride Card allows Kuuga to transform into the Kuuga Gouram, an insect form and giving him the ability to fly. This form is used again in the Den-O to assist Decade and Den-O and allowing Momotaros to execute the Decade Liner Final Attack Ride. The Kuuga Gouram rushes toward Decade with the target stuck in his pincers while Decade performs the Mighty Kick-like Decade Assault flying kick towards the target.
After the card is used, Kuuga can change into this form at will before Decade uses the Kuuga Final Attack Ride Card. In Kamen Rider × Kamen Rider Double & Decade: Movie War 2010, Kamen Rider Kuuga shows the ability to transform into a unique variation of this form, Ultimate Gouram, without Kamen Rider Decade using the Final Form Ride Card. Unique to Kamen Rider Decade is Kuuga Rising Ultimate. Much like Kuuga's other forms that were given a 'Rising' upgrade within the original Kamen Rider Kuuga, Rising Ultimate is an advanced version of Kuuga's Ultimate Form. In this form, Kuuga has a Rider Kick called the Rising Ultimate Kick and the flaming Rising Ultimate Punch. After Yusuke has been attacked by the Stone of Earth used by High Priestess Bishium, putting him under her control and unleashing all of Kuuga's potential: Kamen Rider Kuuga Rising Ultimate. Kuuga's eyes become the Black Eyes, and when Kuuga is freed of Bishium's control, the eyes change color to the Red Eyes.
He later uses this form again in Kamen Rider × Kamen Rider Double & Decade: Movie War 2010 to fight Super Shocker thanks to Decade's K-Touch. Kamen Rider Kuuga Ultimate Form transforms into the Ultimate Gouram, a more powerful version of the Kuuga Gouram, to fight Kamen Rider Decade Fury Form. The Ultimate Gouram can execute the Ultimate Assault, by crushing the enemy in its pincers and rushing towards a hard surface. However, he is soon defeated and becomes a Kamen Ride card for Decade but appears again when Decade uses the All Riders Final Form Ride.