Thank you for your kind feedback!
In general I agonized NPCs disappearing led to Morrowind-like "the thread of prophecy has been severed" scenarios or Genshin Impact's "this character is involved in another quest" problems; so I made it that non-uniques don't disappear. One big problem that used to pop up was the town healer disappearing and your team was half dead with no revives.
Then Author-kun runs into the problem of immersion, therefore the solution is to hang the non-unique NPCs from a tree. From next update onwards I'll put events in the main town area where NPCs are automatically sent to when captured and can be released. Sort of like a mini-brig event with a single CG.
This was already planned for wild captures to make capturing random encounters worthwhile; the game already tracks how many wretches you have captured in the background.
Your post also made me think about the "how close to pokemon" problem, the more I tweak systems closer to pokemon, the more I find it to be the most efficient solution to solving the capture problem, as with many other systems. It's just Author-kun's laziness in not wanting to make Ultra Balls and beyond, but on the back end it is a simple setting of the [Capture Net] event to 50%, and making the [Great Capture Net] event to trigger for 60%.
The "resist capture" thing was also something that myself noted during testing because if you follow the main quest without leveling you run into problems not being able to capture event NPCs, or have the "fear of losing out" on a unique npc. Since that is a feelsbad, I'll have to solve that problem (possibly moving it closer to the pokemon solution). It's also why Rien is a level 6 event instead of 9 now. Thinking...
Flying Onaholes are just the developer's way of saying: this area is in development.
Good stuff, make me think.
P.S: Kino is a scammer in lore, but potions/HP regen code has to be fixed.