Nobunaga, Reona, Yuuto and Kotaro are the four members of the Animal Rangers, led by Hideo. The four of them use their animal-based powers to save the world from the evil organisation X-Ponzu and its leader, Nyaro.
The series is based on a radio show starring the seiyuu Hideo Ishikawa, Nobunaga Shimazaki, Reona Irie, Yuuto Suzuki and Kotaro Nishiyama.
(Source: The Zero Alliance)