There are some things that you can tell your bartender, that you can't tell anyone else in the world.
The Bartender is a mysterious entity who runs The Nameless Bar. Much of who she is unknown.
It is unknown who The Bartender is or where she came from. In a discussion with Matsumi Kaze, she mentioned that she doesn't keep track of her age. What is known is that she seems to both run and own The Nameless Bar, a drinking establishment located somewhere (maybe) in Tokyo.
She first appeared when Matsumi, broken over recent events, somehow wandered into her bar, where she gave the woman some advice, as well as helped her to boost up her self-confidence. It is yet to be seen if others from The Hotel will meet her.
The Bartender seems to have a great deal of knowledge, stating that she knows everybody's name and everything about them.
She has been hinted to have some manner of unknown combat abilities, since she stated nobody has ever stayed in her bar if she didn't wish them to.
Due to the nature of her establishment, she might have some low level dimensional control.
She seems to be an expert in the creation of every alcoholic drink known to man.
The Bartender seems to be a fairly optimistic and pleasant person, stating that she's "always glad you came". However, she has hinted at a slightly darker side, stating that there are rules to follow within the bar, and those who refuse to follow them will be removed without hesitation. She has a great deal of interest in other's problems and always lends an ear to those who are troubled, offering advice in return. However, she refuses to directly interfere in other people's lives, preferring to simply offer her own views on a matter.