Takagi Ryo manga
The story takes place after an abominable war that foisted a "devil's contract" upon a land. Cecily Campbell, a former noble's daughter who joined a knighthood, encounters a man who dispatches some hoodlums with one sweep of a mysterious sword. The man possesses the power of the same "devil's contract" that has become taboo, now that peace has been restored. Cecily has been searching for a blacksmith who can repair an old sword she inherited from her father, and that mysterious young man happens to be blacksmith named Luke. This encounter launches their adventures together.
What would you do if money could be exchanged for life? Sell ten years of life for a fortune, or give up everything to buy one more year. At the age of 17, a high school boy who has it all together meets a man with superpowers that are both godly and demonic. Through a deadly struggle for his life, he stumbles upon a world "on the other side"! Take a cold look at the fixation on human life in this sharply illustrated dark fantasy!