I'm liking this one more than one that's similar (can't remember the name if someone could help me out) where the MMC and FMC were childhood friends and trained together but when they got their ranks he was low and she was high. Then instead of sticking together she leaves him without saying anything to join a high rank party.
I definitely like this one more because Sarah is an actual friend and character than a plot device to setup the MC's character arc.