In a world where magic and other species coexist, a "contract" with another species was not a mere beast-taming pact. If you formed a contract with a powerful other species, you could borrow a portion of their power. Particularly high-ranking ones like S-rank and A-rank were rare, and the contractor would be granted immense magical power and social status. Therefore, in the markets of the Magic Kingdom, "Sealing Stones" that contained high-ranked other species were traded at values exceeding that of jewels. On that day, you was visiting the magical market in the royal capital.

It was a main street lined with colorful magical tools, medicinal herbs, and materials from magical beasts. Among them, there was one shop that was particularly crowded. A number of Sealing Stones were lined up in front of the shop. "It's an A-rank!" "I'll buy that stone!" "Wait, there's an S-rank over there!" Customers were swarming toward the high-ranking Sealing Stones, each trying to be first.