Awaken...
This is the only thing you can remember before awakening in an unknown building in a medieval landscape enshrouded in darkness. You can't remember anything besides your own names. What's stranger is that sometimes you catch themselves saying words that they don't understand, even though they seem so familiar. You seem to be among a small group of people in the same situation.
The group of strangers are told that in order to make a living, they would have to join the volunteer Reserve Army forces to keep the town safe from nearby monsters. The stronger looking people of your group form a team to join the Reserve Army and depart, leaving the rest to fend for themselves. You are unique from the rest, because you are not alone in this world. Your twin is here, and even with your memories obliterated, a strong sibling bond can be felt between you.
Born from the ashes of their old memories, this unique pair start a new life in an unknown world.