He won't have questions for long though, because the next thing Yusuke knows some demons show up and want him to return to Demon World with them. Since all he's been doing is lying low, avoiding Spirit World, and keeping Koenma (who is hiding from his dad. Yeah disobeying dad to save Yusuke is serious trouble!) company he accepts. Of course, it helps that they tell him his ancestor is alive. Yusuke's determined to kill the guy for spoiling his fight. Trouble is, when he shows up he finds the guy already dying! You see, Yusuke's ancestor is a flesh eating demon. And so are most of his men. But he fell in love with a human (duh- that's how Yusuke shows up centuries later) and swore never to eat humans again. So now he's been starving to death over the last thousand years (he's pretty resilient). He's worried, because he is one of the three rulers of Demon World. When he decided to stop eating humans it caused a rift between the three and they divided Demon World equally, so he figures now that he is dying they will try to take his third of the World in order to have the power to take over all of Demon World. He wants Yusuke to train to be his successor. All would be fine and dandy if it weren't for the fact that the other two rulers have found new allies for themselves as well - one has Kurama (thanks to threats on his human family) and the other has Hiei (thanks to the fact that he's... well.. Hiei). So basically it is shaping up to be a showdown between the former team mates (and Kuwabara is left out of this season almost entirely, which didn't bother me much. He's okay though because Yukina is staying with Genkai who died at the Dark Tournament but was resurrected shortly thereafter.) Yusuke surprises everyone by coming out with a plan to circumvent war. There will be a free-for-all tournament to find out who will be the new ruler over all of Demon World. That means both the current living rulers (Yusuke's ancestor died), all their former supporters, and anybody else is allowed to enter. Of course, Yusuke and the guys all enter (they've gotten much stronger) and they do fairly well. But they still lose. Yusuke took a big chance but fortunately the first winner, and thereby ruler, happens to be an old friend of Yusuke's ancestor. His one law is that they have to leave Human World alone. And he establishes that there will be a tournament every three or four years (can't remember, sorry) to decide who will be the next ruler.
After all this Yusuke is going to have trouble fitting in back home. So, while Kurama returns to Human World and Hiei remains in Demon World with the female ex-ruler he had allied himself with, Yusuke decides to stick around Demon World and train for a while - a while which turns out to be nearly four years. Back home things have definitely changed. Kurama is fine, as is his family, and Kuwabara has become an ace student (how I don't know). And Keiko... well, she had promised to wait for Yusuke, but she's not waiting forever. At an outing with the whole gang (Shizeru and Yukina included) she decides that she is through waiting around for Yusuke. Which is fine with Yusuke because... he's there. Keiko throws herself at him and it looks like they just might get their happy ending too. Here's to hoping for our favorite mis-matched couple!