Why do I feel like JBR didn't die. HSJ told him that he had made plans so that both of them could escape the prison. So my theory is what if JBR didn't killed HSJ there and that was all his plan so that HSJ could leave the prison while everyone thinks he is dead. His prison guard friend was either fooled by him or either helped him out as JBR saved his fiance, so he simply repaid the favour. And in the end he simply acted out in front of OBY and KMC so that they believe he is on the deathbed and don't try to investigate much. I feel like JBR also faked his death to escape from the prison in the end too.

That’s an interesting view point, but this undoes the whole series. The writer wanted to give a psychopath feelings and make him realize that what he did was wrong. She wanted to make him feel guilty and have regrets for his actions. 

Ba Reum in the end decided to take responsibility for his actions, which is very brave and not a thing  all of us would do. We many times choose run away from the consequences of our actions but he didn’t. He face them, which is beautiful. And in the end he died not a monster, he became what he desperately wanted since he was a little kid. He died in peace.

Also, if he really wanted to ran away, why he bother to go after OZ? He could have just escape when everyone (almost) knew nothing about him.

Furthermore, if he ran away from prison, where would he go? Everyone in Korea knew him. He would have live his rest life on the run. I don’t think that he had the money and the connections to escape abroad.

 Luffy:

Why do I feel like JBR didn't die. HSJ told him that he had made plans so that both of them could escape the prison. So my theory is what if JBR didn't killed HSJ there and that was all his plan so that HSJ could leave the prison while everyone thinks he is dead. His prison guard friend was either fooled by him or either helped him out as JBR saved his fiance, so he simply repaid the favour. And in the end he simply acted out in front of OBY and KMC so that they believe he is on the deathbed and don't try to investigate much. I feel like JBR also faked his death to escape from the prison in the end too.

That's an interesting speculation. 

Even though the chances are extremely low, there are particular scenes that could contribute to it.

So they explain that the brain transplant isn't really successful cause the mouse this was tested on, ending up dying.

Yet, there's a scene in the spin off "Mouse : predator" where they show that the dead mouse inside the box that was thrown away has actually dissapeared? Did it possibly regain consciousness? 


It could be a hint at how Jang Bareum could actually survive. 

Or maybe it's to hint that the surgery was actually successful therefore Oz will step in and keep continuing the mission. The post credit scene showed a surgeon conducting the same surgery on another patient. Could be related to Oz trying to transplant Jang bareum's brain to someone else's :0

 Trashmi:
Yet, there's a scene in the spin off "Mouse : predator" where they show that the dead mouse inside the box that was thrown away has actually dissapeared? Did it possibly regain consciousness? 

I recommend you to watch the last special (Mouse: The last). There are some deleted scenes from the last episode, and there was a very interesting one. In that scene, that mouse regained its consciousness. Who knows, maybe Ba Reum survived too, but I don't think we will ever know that for sure. 

Perhaps, after the block of the drama in Series Mania Festival, we will know more things about the ending but i don't think so. I think it will be tha real mystery of the show.