I encountered the same issue. What I did was I grabbed a 100% save file online. After applying it, go back to the last map movement choice you made, and CTRL forward. (You have seen all of this already, so don't worry about missing anything.)
Now with the 100% save file you should get a non-map movement choice all the way at the end. One takes you the normal ending you have just seen, and the other to the true ending.
The true ending choice is:
Here is my save file if you can't find any.
Just put it into the game directory>save data and overwrite the your current file.