River

underworld office is a small information room on the underground station. All ghosts in here doing good things to supress their evil deeds to don't become a monster and guard the border between human world and underworld.

Hayden (a ghost of 6-years-old boy in cute hat, curious and happy) - in a good relationships, always ready to chat
Joan (a ghost of old woman, serious and hard) - most neutral, but sometimes can argue about some things
Boss (a ghost of man, serious, mysterious and not really talkative) - very complicated, she depends on him because he knows the only way how to become clear and finally find peace in underworld. She's like his "dog", doing all his commands. Sometimes they irritating each other, she can made a very sarcastic joke about him
Eugene (a mortal, his soul leaves his body only on night so he becomes a ghost for a short time, a little shy, but kind) - good, likes making jokes on him, but always ready to help in danger if he calles her
Charlie (a ghost who used to be evil spirit, but then get caged in Joan's keepsake and lost all their memory, sharp, sarcastic, pessimistic, but has a good sides) - thinking that they are very similar, clearly likes them

River's keepsake is kept a secret throughout both games, but at the end of Charlie in Underworld, it is revealed that River's keepsake is her hair.

It is unknown as to why or how her hair is her keepsake. A significant amount[1] of her hair was ripped off and kept by Boss so that she'd have no choice but to work for him. In Chapter 7 of Charlie in Underworld, when River became a powerful evil spirit, whenever Charlie touched River's hair, it would force them to revisit displeasant memories. There is a slim chance that it is a reference to the quote "Hair holds memories".

River has almost full control of her hair, so she can use it as a weapon and for self-defense. It is also used for support and keeping her enemy in place.

River is a tall and slim woman with long hair. Like Boss, she has a purely black-and-white body in order to distinguish the dead from mortals. The upper portion of her hair is black while the baseline is white. Aside from this, the only white parts of her body are the entirety of her arms, her neck, her ears, and the lower half of her face. River is the only Underworld Office employee who does not wear a shade of indigo.

River acts like a free spirit. She wants to have fun first and foremost, which often makes her impulsive. She would even willingly risk gaining more misdeeds just to fight bad people she sees randomly in the streets. River also enjoys teasing people and getting in their nerves, usually with Boss, who is easily annoyed by her antics. Despite this, River cares for her friends immensely, as evidenced in her interactions with Eugene. She is also not as mindless as she appears to be and acts mature when it counts.
As a human, River was hardworking and dedicated to her job, even though she wasn't given the appreciation she deserved. She is depicted to also have a teasing personality when she was alive as well, still bantering as much as she does now.