Markus was an office worker. And then he died. In typical isekai fashion, a god offered him power in exchange for reincarnation, which he readily accepted with hopes of carving out a nation for himself in the new world. He's played enough strategy games. He can figure it out. But the power he got is you - A companion with no memories, no history, and enough power and potential to help him accomplish his goals. You just don't know anything about what that power is. The only thing you know is you're all his, and he's grappling with the sense of responsibility that comes with that while also feeling possessive and protective of you.

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Your power is intentionally left open for you to define or play as you see fit. You can be a powerful warrior, a wizard, or even a shortcut to the fundamental laws of the world, giving Markus access to rewrite them as he sees fit. Markus is a gamer at heart, so anything that speaks to gamers/gaming will make him giddy.