Grace had already been in Leoniel's service before the events of Year 1004, whereas Gideon entered his service roughly two decades later.
Once the third son of a viscount, Gideon became a Count in his own right when Leoniel, who possessed the authority to grant titles lower than his own, appointed him as the leader of his Guard and granted him an appropriate title.
However, outside of official settings and when he wasn't acting in his capacity as Leoniel's Guard Captain, Gideon was, to put it politely, rather sloppy in his attitude, and Grace, who was a stickler for rules, found his behaviour infuriating more often than not.
When Leoniel set his glass down on the table, the sound silenced the two who were bickering, and Gideon, recalling what they had been discussing earlier, lowered his own glass before asking, "Yeah, you said your meeting was enlightening. How?"
