So the rings were scientifically developed as a weapon to reverse the hormones of influential men from other nations and turn them into girls, along with the awareness/perception (reality) of their existence. Not what I expected.
Asui Rin was a nobody janitor with no living relatives, working for the lab that developed the rings. The lab had perfect security designed to protect against rival nations, but they never expected a janitor from the inside to steal the rings. Rin says he's stupid so he didn't understand what the ring's power to change reality meant, but it conveniently removed him from the security camera footage. The rest is as you can imagine. Asui Rin just wanted to see if the other guys who received the rings were able to 180 their lives from despair into happiness and success. They very much did.
The story ends with Rin giving a ring to another guy, presumably the reader.