Collect Debt for Teacher

The master passed away, leaving behind a broken account book and a sentence to the fifteen-year-old accountant - "After collecting the debt, you will know who the master is." She thought it was a hard job of collecting bad debts for a poor old man, but all the way, the people who knelt down to pay off the debts were giants from the three realms. She gradually discovered that what Master never remembered was money, but grace, life, and everything the world owed him; and her own name was written on the last page of the account.