Su and Yan_(gyee) were childhood sweethearts who grew up in Kaigon together. Kaigon is the mecca of Ka. Because Ka's tolerance and protection of Gyee, the White Capes dare not intrude, so many Gyees made the city their home. Every major faction would visit Kaigon and recruit talented children. When he was 10 years old, Su was picked by the White Turbans to stay in Kaigon and learn magic. Yan was selected by the Shadowhunters for training in Westhold. The pair made a pact to reunite in Kaigon after their decade's training is up.
Finally, the ten years were up. Su waited for Yan in Kaigon when he got a letter from Yan that he had received orders to defend the altar on the island of Broken Toe, so could only see Su at the dock. Su rushed out of the church but got there just as the ship left port, leaving them to stare longingly at each other.