First off, I think its okay to say that this isnt a straight forward plot and easy to get. Its actual really frustrating the first time reading it because Its so confusing. I was so angry too because I didn't get it but after kinda reading around you get the idea. Please regard this is also MY interpretation but I hope I can help someone out and avoid the feeling like reading this was a waste.
1.) Since the beginning the hidden relationship between Law and Jesse was that Law thought of Jesse as a God and Jesse saw Law as someone manipulated and controlled by his parents. All Jesse wanted was Law to be sincere with him. So one day when Jesse asked what Law wanted for himself and he said "to be treated as an equal"
- They were both mentally unstable and didn't really know what they were feeling towards each other
2.) then when Law's parents died two things happed. First, Law consciously thought that he was free from being controlled from his abusive parents and allowed Jesse's parents to use him in their business. Because of this Jesse misinterpreted Law's rejoice and something his mother forced him to do. Which caused him to ban him out of the house in order to keep his word on treating Law like an equal.
3.) 5 years passed after Law was banned. During that time a scandal created by Law breaks out which puts Jesse and his family's company in a tight spot. (Rosalie saying she was being used as a lab rat at the brown company; Making Jesse take the blame) Law then strikes to take revenge on Jesse.
4.) He uses his blood clot disease as a way to trick him into using Moritat.
Once inside Moritat Law thought that if he forced the idea that he was all Jesse had left, Jesse would rely on him making him feel better of himself. (killing his parents, the part where he was raped and convincing him that the maids and butlers know nothing)
5.) it wasn't always successful. Jesse always rejected him and never trusted him. Law then tweaked the program every time he failed. This felt like 20 years to Law but in reality it was only a day (Thats why Jesse said he never aged and Rose was always clumsy)
6.) In the end Jesse thinks that he forced Law to be with him by force. He thought he Law already died and he created the virtual world because when he woke up Law would be gone. He feels bad and says he's willing to die with law instead of sending him off.
7.) Because of this Law goes into a sort of internal panic which causes him to confess everything to Jesse and turn off the system. Law tries to tell Jesse that "I got tired of you so I guess the pain went away" when in reality he got scared that Jesse for the first time treated him as an equal or finally relied on him.
8.) In the end Jesse finds Law still looking at a virtual version of himself and realized Law "liked to be controlled" but only if it was Jesse doing it. (Thats why he said in the end "You were that type of person after all")
9.) Jesse tells Law to stop replacing him with the virtual "What if" and comply with whats already a reality. Its never certain but thats okay since their relationship can't just be "deleted" or "erased" like in Moritat
This is a link to a english Q&A from the author. They explain some stuff like the ring meaning and more about the characters arc. (also a bit about the animation itself) Wahh on a side note it also included how Myeongi apparently has a little sister (I think thats just really cute thing to think about)
https://monoreille.tistory.com/10
This author has so many heart felt and emotionally touching stories :-; Every single one of them are so wholesome and I love all of them so so much. They are so short and sweet and I just wish there was more to them