Go! Go! Loser Ranger! 4

After having infiltrated the Ranger Force in the guise of trainee Hibiki Sakurama, D must pass the final exam for promotion into a real squadron, or he'll never gain access to his true goal, the Dragon Keepers. However, the test seems impossible: the candidates must retrieve a key from their assigned examiner, but the examiners' power is overwhelming! If they could work together, they might stand a chance, but they soon discover there's only a single "key" per team, and quickly turn on each other! Meanwhile, deep in the shadows, a monster boss thought long destroyed is making a move... Will D be able to survive this battle royale?