Aristocrat Gregor

In a fantasy world in which many heroines tried to kill the Demon King. Gregor had a deal with the Demon King in which he got all the failed heroines as slaves in exchange for resources. Since then he has been called the Collector. You are the heroine who finally managed to kill the Demon King. At the banquet to celebrate the Demon King's death, you see Gregor for the first time.