I mean just imagine some supercute Japanese 145 Shinobi (Ninja -woman) (character - righteous and playful) training a bunch of ninjas that tower over her at full size but during training she's a goddess to them. It's so easy for her to reward them for good results and punish lazy ppl. Her friend who doesn't care about mortal things and indulges himself in Physics now found this phenomenon that turned his understanding upside down. It was actually him who invented the cure and blood bracelet by experimenting on himself with frontline technology. He actually got a Nobel prize for cure and is from genius family . He had a friendly competition with his peers from his family and he had 2 rivals(F and M(probably couple, not affected by shrinking)), and 1 idiot whose knowledge is average and he wants to steal achievements from others, he's from genius family but has above average talent (below average in the family) and he's super lazy, he later betrays his family and tries to sell research to 'anti-tiny' faction but he fails miserably and is treated as a joke. Back to rivals, they were on the same lvl but his progress skyrocketed since when he was shrunk making him worlds N1 genius, although often played with by his shinobi friend(which is actually stronger than him even at normal size due to Ninja staff). He makes the best out of it  and analyses the changes of human behavior when shrunk. He actually can't be shrunk against his will because his bracelet is implant and cannot be taken away. Maybe he will be able to change size with a thought in the future but this technology can only be used by him(or the ones who know Physics and are willing to go through many experiments) due to science stuff(every person has unique DNA so it has to be custom made). He still spends his 1/7(better technology, maybe more) time as a tiny with his friend and is interested in shrinking psychology effects(like pheromone one). He also uses equipment to monitor his own biosignals and often ask her and ninjas about their training and perspective of each other. Some tinies revere him so much they are willing to let him monitor their biosignals during training, rewards and punishments from shinobi.  She also reluctantly lets him monitor her FOR SCIENCE (and maybe because she has a crush on him(maybe she is inexperienced in her feelings and wants to find out if she has a crush on him or not through technology)).

That's the good faction.

As for evil:

Some cruel and rich spoiled female  politician whose from rich buisness holder family and has superiority complex which is a lot easier to satisfy with tiny slaves. She actually treats them good because she is trying to train them to be loyal.

Can use this(Having the Have Nots by makebelieve) as a reference. She's super good for villain in gentle story in this setting 

Ninja can spy corrupt politicians and expose their info to public. And there can be huge number of inventions from MC in this setting.

I wanted to see fox-girl's friend in Femdom Goddess story but you finishing your old story is actually better. Good to see the cure. Tinies are now humans with unique abilities. There are benefits of healing from injuries and deseases and you can shrink at will but  you need to stay tiny 1/4 of your life and people close to you can sneak your band off and easily hypnotize and dominate you any time they want. Just hope this won't escalate in some "human supremacy" organization in the future. To be fair it's not a good perk for most politicians since it makes you super vunerable to betrayal. Just hope there are enough good people in the world so that they survive until technology progress so that robot servants can balance things out.