all of the branches have canon managers! the three you listed don't have canon names but they do have somewhat formed personalities. zoo's is a motherly lady who loves to eat and considers everyone who comes to her branch her children, but is also somewhat intense and eccentric, for direct reference see episode 9 girs crisis. the megallanica branch manager is an idol manager-type guy, huge fan/supporter of idols and kind of a nerd? see episodes 2-3 girs crisis for him. and the star gate one appears to be a gaming/gundam nerd who's negligent with his duties in favor of playing video games; he appears in passing in episodes 12-13. i really recommend watching girs crisis if you are writing something like that, it's a fun season that really goes further into how fiva operates + you get to meet am and luna which is always good. another rec would be episodes 1 and 2 of gz, they all gather for a meeting in those -- they also all appear in episode 50 of stride gate but they're fairly generic/stock appearances with the exception of satoru for obvious reasons. hope this helps?