Masao Den is a former officer of the National Defense Ministry and the designated leader of the Battle Fever team. He is a highly skilled martial artist, particularly excelling in judo and karate, which heavily influences his disciplined and effective combat style.

As Battle Japan, he is armed with a specialized combat spear to strike down his enemies. In battle and during the team's signature roll call, he incorporates a unique, kung fu-inspired dance into his movements, allowing him to channel his rhythm and momentum against the forces of the Secret Society Egos.