Azaroth was oblivious to Shun's planning. Actually, this sort of information was a closely guarded secret that only the ruler of a Kingdom would know.
Shun found out about this information through pure coincidence when he was reading the ancient records of the Sinyalian Kingdom.
The Saint Stele was briefly mentioned in those ancient records, and Shun remembered such a stone stele in a secret chamber of the Royal Palace.
He then met with an archaeologist specializing in ancient history and authored books about it. This was the same archaeologist who had deduced the truth about Azaroth's totem.
This archeologist had many theories regarding the ancient era and also mentioned Saint Stele. His theories regarding the Saint Stele matched up with Shun's guesses.
