"Opponents needed! Do you have what it takes to train with the Imperial guard?"
"Practice battle maneuvers with the Adrestian Empire's Imperial guard."
Quest-Giver Dialogue 
"The Adrestian Empire's Imperial guard is looking for someone to train with. They're said to be the cream of the crop, but I'm certain you can hold your own."
Quest Completion Dialogue
"Professor, I know it was just a training exercise, but I can still hardly believe you defeated the Imperial guard. That was thrilling! They were so imppressed, in fact, that they decided to support us here at the monastery."
Given to you by a male soldier near the Knight's Hall.
Subjective: The following part of this article is based upon the editor's personal experiences and opinions, and therefore may not be applicable for all readers.
Talk to the soldier near the Knight's Hall and accept the quest.