The Hanged Man is the 12th of the 22 major Arcana in a tarot deck. He first appears in Julian's route, during chapter 2 of Book XII - The Hanged Man. Of the other Arcana, he is the most difficult to see. It is very difficult for magicians to travel to his realm, and for a person without magic to see him they would have to have a near death experience. When Julian "dies", he is then in the realm of The Hanged Man. The MC is also there, but they cannot interact with Julian. Instead, they can only hear the  conversation between Julian and The Hanged Man(in which, he is aware of your presence). You end up learning that The Hanged man was the one who told Julian the cure to the plague, and that he was the one to give Julian the magical mark on his throat. He gives Julian two choices: one of which to stay in the same realm as him and learn as his apprentice, or to use the remaining magic left from the mark to be resurrected. When the MC tries to interfere, The Hanged Man looks at them and gives them a signal saying "it is not your place to interfere, it is his choice." He also gives Julian back his memories from 3 years ago