Royal Card Legend: Obtain the Legendary Monster Cub at the Beginning

An Yu, an 18-year-old boy, traveled to a different world where magic cards were used. At the beginning, the strongest monster left a cub in his body. With the monster in his body, he grew up to become the strongest card master. Does the enemy have a nine-star magic card? Is the hostile force an entire country? Don't worry, the princesses from the remaining three kingdoms are all my friends, and I can also make their nine-star magic card. This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.