Traveling Through Two Worlds with the Glory of the King

If you could choose a system, what system would you want? What would you do if you had a magical world? If you could only choose one, which one would you choose? Only little kids make choices, I want both. I, with the system, traveled between the two worlds and trained my sister to become a boss in the world. PS: behind the scenes flow This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.