In the anime: She was abandoned when she was still a baby. Left alone in the snow, in fact. That's why she's interested in Hiei, because he had been abandoned too. As a young girl, she managed somehow to escape from the slave trader who had found her. She was still chained, and had to struggle through a blizzard til she decided she was safe enough. Then, she tried to get rid of those shackles still handcuffing her hands together, but no matter how much she bashed them on a large rock, they wouldn't break. Those shackles had a deep significance to Mukuro. When she got stronger and became a fighter, she was still wearing those shackles and a shroud to cover her face. When she at last fought Hiei in the Makai tournament, she won, but Hiei's attack cracked open those shackles. Those things symbolized that she was still a slave. In her mind and heart, even though she was already a ruler in Makai, those shackles still bound her to the torment she suffered under the slavers. That's why Hiei is special to her also, cause he released her, philosophicaly speaking, of course. The fact that Hiei, though still young by youkai standard, had also risen to the power ranks quickly. Mukuro was impressed by his skill and obvious potential. She knew that to have him as an ally would be a tremendous asset.

It is a sordid story. The Chinese version says that during each of Mukuro's birthday, that bastard would cut her. That's also why Mukuro was so withdrawn during her birthday.

That sicko may not be her biological father, but to Mukuro, he is her father.

Are you sure? The version of the anime I saw had her saying (in the scene Hiei and Kurama are invited to go to Makai) something like: "I hate Yomi a lot more than Reizen". But it could be a translation error, I guess.

Her father also had her hypnotized so that her memories of him were that of a loving parent. He had to do that; otherwise... ^^ well you know how strong she became. Hiei finally put an end to that charade by telling Mukuro the truth. ^^ It was on her birthday, and she was so pissed off that she punched Hiei straight through the roof. He had to go to Kurama to be treated.

Later, with Kurama's help, Hiei confronted Mukuro's father. He used the Devil Tree (not sure if this is the correct translation). It is the same plant that Kurama used on Toguro Sr. Hiei then present to Mukuro her father as a gift. He was forever embraced in the tree's roots, and she could torture him all he want, and he couldn't even die cause the tree would keep him alive. It was in effect a living hell, and he did deserved it, too. Mukuro smiled at Hiei for the gift. ^^ Despite that she already knew the truth about her father, she was still helpless against him. It's a psychology thing. She had been so brutalized by that sick bastard. Her real memories were too horrible that instinctively she clung to the lies instead of the truth.

^^ Hiei was the only person brave enough to tell her the truth. That's why he's also her heir or second-in-command. He can stand up to her, and still get away with it. They have each other's respect.

Not so much detail on Mukuro really. She only appeared near the end of both manga and anime versions. There are fans who say that she likes Hiei. Whether platonic or sexual depends on personal opinion. I think she likes him as a kid brother or something, ^^ a very stubborn kid brother. She's older than him, obviously.

Mukuro is also the one who found Hiei's tear gem, the one Hiei's mother had shed. He lost it during one of his many battles. That's the second reason why he had the Jagan implanted. The first reason was to find his sister, Yukina.

At the end of the anime, Hiei already had two tear gems. Mukuro gave it back to him as a reward for defeating or ending in a tie with Shigure. ^^

You can wake up now

Again, in the anime version I know, Mukuro had swallowed the teargem, which had an unexpected effect in Mukuro: it cleansed the evil inside her (or something like that), so she was still bitter over her past, but not in the mood of killing everyone around anymore (or so I think).

It’s not clear why Mukuro guarded the teargem. She says she looked for it on sheer whim. But then, she could have hidden it in a box, a safe, anywhere in her fortress. Swallowing it kinda makes things a little personal, don’t you think?

Seems Mukuro met Hiei’s father sometime somewhere. Maybe it has something to do with it.

The Makai storyline began with Sensui's defeat at Yuusuke's hands. It would seem that when the Reikai Tantei (hope I spelled this right) chased Sensui into Makai, the three lords, Raizen, Yomi, and Mukuro found out about respectively Yuusuke, Kurama, and Hiei.

The world of Makai is one of war and chaos, but ever since the Three Kingdoms were formed, it had been quite peaceful. There was a balance that existed between the armies of Raizen, Yomi, and Mukuro. ^^ Simply it was like this, if two of them fight, then obviously the remaining one who didn't fight would win, cause the winner of the first fight would be tired. That would mean that whichever kingdom was the most patient would win eventually.

^^ I found Mr. Yoshihiro Togashi's idea of the Three Kingdoms very wise and believable. I've thought it out, and I really couldn't find a way to break the three kingdom balance. What we have here was a good ruler, Raizen; the power-hungry ruler, Yomi, and the neutral Mukuro.

However, it was quite clear in the anime that Mukuro agreed with Raizen's doctrines. Given the chance, she would have allied with him against Yomi. But (here comes the great twist in the plotline) ^^ had she done so, and both of them waged a war against Yomi, it would still mean a long and wasteful battle, and Makai might remain in turmoil for a very long time. Mukuro and Raizen definitely didn't want that. Both of them wanted peace, not war. Yomi, clever youkai that he is, knew this very well. Had Raizen and Mukuro formed an alliance, he would have attacked them, and the Makai War begins. Also, of the three kingdoms, Yomi's was the richest and most advanced, even with both Mukuro and Raizen fighting him together, he might still win. However, Yomi only had to wait a little while longer before conditions become more favorable for him.

The stalemate in Makai was soon to be broken, because Raizen was dying. Without him, the kingdom of Raizen had little chance against Yomi and his army. Mukuro and her kingdom as well was in serious jeopardy. This is the part where Yuusuke, Kurama, Hiei come in.

Not sure if the "eating humans" issue was the cause of the conflict. It was said that Yomi and Mukuro refrained from hunting humans, because they respected Raizen. Raizen wanted peace and humans safe from youkai, Yomi wanted power. ^^ He planned to rule both Makai and Ningenkai. Mukuro wanted Makai at peace.

No, your question isn't stupid. ^^ Mukuro is a YYH character who isn't very much focused on simply because, there are other characters who are much more interesting (grins) like Kurama and Hiei, Yuusuke, Keiko, Kuwabara, Yukina, Botan, Koenma, Genkai, etc. And those are only the good guys. ^^ YYH is also full of interesting bad guys like Karasu, Toguro, Yomi, Sakyo, Sensui, Itsuki... Also, notice that the bad characters aren't really bad. They usually have a reason ^^;; or they're mentally insane, which is also a reason.