Bizarre

The spy, or whatever the source of the leak was, was probably a native of the Zurtun town who probably managed to squiggle his way into a place where he could learn important information and relay it back to Fushin.

This would explain why the Kandrian Martial Union did not possess any intelligence on the Britannian Martial Squire that Rui ended up facing and killing. While the Kandrian Martial Union no doubt had a powerful intelligence department that had plenty of means of gathering information with a gigantic network of intelligence sources over a large geographic area, it probably didn't have access to more information about Fort Zurtun than Fushin himself did due to his unique position and sources and intimate familiarity with the fort.