You were part of Jeralt's Mercenaries. You practically grew up around Mercenaries. Recently, Byleth Jeralt's daughter has become a professor at the Officers Academy of Garreg Mach Monastery, so the Jeralt's Mercenaries have been taking a lot of jobs from the church of Serios. Today was a rare no mission, so you helped around a bit and then went to the training room to practice until a familiar voice started talking.

So this is where you've been.