Daigoro Kumano, also known as Kirenger II, is a character introduced in the latter part of the series. His background is that of a promising young member of the EAGLE organization, specifically from its Kyushu branch, where he served as a reserve member. He is selected to become the second Kirenger, the Yellow Ranger of the Gorenger team, because the original Kirenger, Daita Oiwa, is promoted to become an instructor and commander of the Kyushu branch. This makes Daigoro the first replacement Ranger in the history of the Super Sentai series.

In terms of personality, Daigoro is characterized by a reckless and headstrong nature. He is notably skilled in sumo wrestling, which contributes to his physical fighting style. His personal preferences include a fondness for sweets and fishing as a hobby. It is also mentioned that he has a great love for curry rice, reportedly able to eat six large bowls in one sitting. His reckless personality is a defining trait that directly influences the events of his story arc.

Daigoro's primary motivation is to fulfill his duty as a Gorenger, upholding the team's mission to fight the Black Cross Army. His role in the story is as a temporary but active member of the main cast, taking on the duties and powers of Kirenger. He inherits the nickname Dai-chan from his predecessor, though his teammates Tsuyoshi Kaijo and Akira Shinmei often call him by his first name, Daigoro. He joins the team for their missions, piloting their mecha and fighting alongside them against the various monsters sent by the Black Cross Army.

Key relationships within the team are built on his status as the new member replacing a beloved comrade. While he is accepted and works alongside the other Gorengers, his tenure is marked by the need to prove himself in the shadow of Daita Oiwa. His development is tragically cut short. His reckless personality leads to a critical mistake during a battle against the monster Can Opener Mask. In this fight, he is fatally wounded when the monster's weapon, the Can Opener Cutter, stabs him in the abdomen. After being shot by enemy soldiers, Daigoro becomes the first main Super Sentai hero to die in the line of duty, and notably, he dies while still in his transformed state as Kirenger. This event leads to the return of Daita Oiwa, who resumes his role as Kirenger to avenge his fallen successor.

Regarding notable abilities, as Kirenger, Daigoro possesses superhuman strength and is a capable hand-to-hand combatant, with his sumo background being a particular asset. His primary weapon is the Ki Sticker, a staff whose tip can change into different forms for various attacks. He also has access to the standard Gorenger arsenal and equipment, including the Birdies explosive weapon, the YTC radio communicator, and pilots the team's mecha, the Varidreen.