To transport the Magic Stone to the underground, it was necessary to destroy the defensive magic array, but once the array was gone, so was the protection for the research institute. In such a situation, the entire institute would be as exposed to the Demons as a naked young girl, which is why the Guard Corps had to be dispatched for defense.
Rocky had originally thought that he could easily handle everything this time, but it turned out that battle was still inevitable. Therefore, after that, he took the opportunity of returning to Sky City to discuss the plan with Karina, and they finally made it back to Sky City.
Upon returning to Sky City, the two wasted no time in arranging manpower. On the one hand, they made sure their respective troops were ready for combat; on the other hand, they moved a large stock of Magic Stones from the storage and loaded them onto the transport ships.