This version of HAL21 specifies a Japan release, indicating it might be a region-specific variant with potential differences compared to other versions. However, the lack of readily available information makes it hard to confirm specifics. More research into Japanese arcade game archives would be beneficial to unearth more details about its release date, developer, and unique features.

HAL21 (Japan)

Hacha Mecha Fighter (19th Sep. 1991, unprotected, version Thunder Dragon conversion)