Undercover Cops Gaiden - Hakaishin Garumaa is a Game Boy action game from Japan, possibly a spin-off or side story. The title suggests a focus on undercover police work and combat against a villain named Garumaa.  Typical Game Boy action-game mechanics are likely, such as side-scrolling, beat 'em up, or similar styles. Further research is required to verify the developer and publisher.

Undercover Cops Gaiden - Hakaishin Garumaa (Japan)

Ultraman Chou Toushi Gekiden (Japan)