I Use My Lifespan as Currency

A pound of pork costs two hours of your life. One taxi ride costs an hour of your life in fare. This is a world where everyone can live only until the age of 28. If you want to keep living, you have to earn more life through work or by hunting demon beasts. The good news: when citizens turn 28, their physical abilities and appearance are permanently frozen at that age. The better news: if you can keep earning life to extend your lifespan, you can achieve a different kind of immortality.