Yuusha Shoutai Kamoku Yuusha Wa Nagisa Renai

An introverted Otaku was summoned to a Fantasy world, and successfully defeated the Demon King there. Just before the ritual to send him back to Japan was complete, the country's Princess dashed into the middle of the spell to be with him. When they both opened their eyes, they realized they were transported to a Sci-Fi themed world than neither of them recognized. Working together, they must now survive in an unknown world and find some way to get home.