Blade Master

 Blade Master is an arcade game made by irem corporation, back when they were cool. As usual a demon army is invading some far off fantasy land, and only the Princess Emina can stop it. Unfortunately she is kidnapped by that very demon army, and it's up to her brother Arnold and his best-bro Roy to save her. After cutting a bloody swath through the army they discover that Amina has been turned into two(!) naga who then attack. They deal with her they same way they dealt with everything else, and after being defeated Emina returns to normal.