Identifying Fantasy Novel

I’ve been looking for an audiobook I listened to a couple years ago and can’t for the life of me figure out what it was.

It is a fantasy or litRPG and the premise is a young kid that shows up with no back story who is very weak and naive (I know, narrows it down, right?)

The only part that really stands out to me now is that after he is adopted into the military academy he is told to run by his instructor, who is one of the main characters, and he continues running because he is not told to stop. The female protagonist that is his age is mad at the instructor for it and she is with him the majority of the book. It seems like there was also a scene where the protagonist falls into a pit when marching with his squad and then later meets up with them when they are under siege in an abandoned city.

I feel like the key is that he is SO clueless, weak, and naive when he first shows up, to the point he’s almost an automaton.

This has been driving me crazy and AI can’t seem to identify it for me, so any help would be greatly appreciated.