Dying star?

[Flying Arrow]

Maybe the characters are battling some time way, way, way in the future. Reminds me of Gene Wolfe's Book of the New Sun, which is set on an Earth so far in the future that the sun is red and our own modern-day metropolises are crushed sediment and glass on Earth's beaches. If it's worth anything to anyone, Amano did some illustrations for the covers of the Japanese editions of Book. Not that it matters in this particular case, but it's an interesting coincidence. Also, Castlevania: Symphony of the Night contains a direct reference to the main character's ceremonial blade - so there are certainly Wolfe fans over in Japan's game development industry (or there were in the mid- to late-90s at least)!