Because there is an anime and manga, their fates are set in stone in different universes.
In the anime, Mine died first and then Tatsumi. They were both trying to stop members of the Empire and succeeded at the cost of their lives.
In the manga, Mine was injured and had to retire, but when the Empire was defeated and new order was established, she moved to Tatsumi's village with Tatsumi, who was permanently stuck in the form of a draconic beast. They also had children in the epilogue.