Yusuke Urameshi
He's a 14 year old brat who goes to Sarayashiki Middle School. Yusuke has the rep of being the toughest guy in town, and gets into fights constantly. He has this other side to him that is completely opposite from what others know of him. Yusuke was hit killed by a car while saving a kid who ran out into the street to get his ball. He became a spirit who had to wait to go back to his body since he 'wasn't' supposed to die. So in the mean time, he works as a spiritual detective with Botan.
Botan
She's a messenger from the spirit world who rides an oar. Botan is the ferrywoman of Sanzu River who guides new spirits (kind of like a cross between the grim reaper, and a river styx). She's helpful and 'perky', but at times, useless to Yusuke. Koenma gives her the job of assisting Yusuke on his adventures.
Kuwabara
He's Yusuke's top rival. He and Kuwabara fight everyday, and everyday, Kuwabara gets beat up. He craves to be the best and won't stop until he finally beats Yusuke.
Hiei
He's a demon who befriended Yusuke. Hiei is a master swordsman that is incredibly strong and very quick. He has a magical third eye that is covered by his bandanna. Hiei doesn't truly care for other humans, but when others respect and help him, in return he offers complete loyalty.
Kurama
Like Hiei, he is also a demon, but in human form. Kurama is over 300 years old and very wise, but at the same time a very ruthless, powerful warrior, who is completely merciless. On the upside, he's quite calm and content with his surroundings.
Kayko
She and Yusuke grew up together since they were little. Yusuke loves her but won't admit it. While Yusuke's soul is separated from his body, Kayko helps Atsuko take care of him. She's the type of person who'd risk her life to help others in need.
Atsuko
She's Yusuke's unemployed and alcoholic, single mother. Atsuko tries to help him make wise decisions, but with her mood swings and drunken temper interfere with her parental skills. She hopes that Yusuke makes something of himself and not end up like her.
Shizuru
She's Kuwabara's older sister. Shizuru tries to help him go in the right direction, but if he stumbles the other way, she beats him up.
