From Arcade Studio:
The monsters invented and developed a terrible jumping-biting semi-atomic bomb and threaten to destroy PacLand if its inhabitants will not send them tribute - 500-ton piece of cheese. The best super secret Agent Chewer is dispatched to find the monsters. He is so secret that even he does not know that he is a secret agent. So hunting for monsters begins, Agent Chewer follows in the track of monsters that leave a lot of cheese bits. His purpose is to find and neutralize their terrible creation - semi-atomic bomb.