The series revolves around vampire hunters who must use sunlight-based weaponry to combat evil undead creatures.

This was stated by one of the game's producers to be due to its more drastic changes from previous entries and the fact that it was a soft reboot.

[5] Lunar Knights revolves around dual protagonists, Aaron, a hero equipped with a solar gun, and Lucian, a sword-wielding "vampire killer" who gains power from darkness, as they seek to free the planet from the hold of tyrannical vampires who have covered the world in a false sky.

[5] Jeremy Parish of USgamer called Boktai similar to a mash-up of Metal Gear and Castlevania, although remarking that there was more to it than this, as the games also drew heavily on spaghetti westerns.

He called the requirement to charge the player's gun using actual sunlight "baroque and complex", and an "extreme solution", but "perfectly fitting coming from Hideo Kojima, a man known for his love of manipulating audiences and breaking the fourth wall".