It is an upcharge. I can't remember how much, 500 yen, tops.
You start by giving your ticket to a nurse or orderly in blood spattered hospital gear. After waiting in the dark lobby for about 5-10 minutes your eyes begin to the dark and they move the group (usually about 10-15 people) into the next room. Here you watch a movie (In Japanese) that gives the rules for the attraction and sets up the story.
The first time I did this there was a story about horrible unnecessary surgeries and the subsequent results. This time, the story was more supernatural. I don't know if the movie is selected randomly or changed periodically.
Next the group is walked to the next waiting area, where you are broken into groups of 4 or less. Each group is given a single penlight.
You have your group photo taken and you are given a reciept to look at your picture later.
Then the fun begins. There are branching paths. There are live actors. (Lots of 'em!) There are countless props from hospitals from real body bags to infant incubators and x-ray machines. You go through OR's private rooms, ER, and of course, the morgue.
It takes upwards of 30 minutes to get through, and the best part is the actors seem to delight in chasing shreiking Japanese girls well beyond the range of their zone! I had one guy follow me at least 50 feet down a hallway, setting me up pretty good for the next guy.
After the exit (there's more than one way out) you enter a snack shop and souvenir store where you can look at and purchase your photo. The shop attendants are also in bloody scrubs, so they might be actors on break. This shop carries the breast pudding cups, if you are looking for them!
Hopefully that was spoiler free, I tried to avoid details, and I'm not sure what you see down some of the paths.