Despite being the only human member of Yu Yu Hakusho's main quartet, Kazuma Kuwabara has proven time and again that he's just as brave as the rest of the gang. Because of his spirit awareness, he's helped Yusuke numerous times despite their intense fighting rivalry.
Kuwabara has seen the worst that both the Demon and Human worlds have to offer, yet he was still able to get into a good high school. While he's helped out numerous times throughout Yu Yu Hakusho, here are some of his most heroic moments of them all.
When Kuwabara Helped Save Keiko From a Fire
While Yusuke opened the pathway for Keiko to escape his burning apartment, Kuwabara was going to jump in regardless of the danger involved. He had no idea that Yusuke's ghost was there or that he would throw his spirit beast's egg in to help push the flames back. Kuwabara was simply willing to risk his life for Keiko and Yusuke's then-lifeless body and would put his own life on the line many more times in the future. Luckily for everyone, Yusuke's ghost was on hand to help save everyone this first time.
When Kuwabara Jumped Into a Demon World Portal
After going up against Rando at Genkai's tournament, Kuwabara was still willing to jump into a portal leading to Demon World when Makai insects were beginning to infect people on Earth. He had seen how powerful demons actually were, yet he still chose to go up against some who were even stronger than the one he had already fought.
Yusuke was the Spirit Detective and it was his job, but Kuwabara volunteered because he cares deeply for his city and wanted to protect everyone. He took down the Saint Beast Byakko so Yusuke could save his energy for the final fight against their leader Suzaku.
When Kuwabara Let Toguro Stab Him in the Chest
Kuwabara was willing to fake his own death to let Yusuke reach his full potential during his Dark Tournament fight with Younger Toguro. At the time, he had no idea that Toguro would purposefully miss his vital points, and it was only after the attack that he came up with his plan. He told Kurama to play along because Yusuke needed some "good shock treatment."
Toguro had no problem killing anyone who got in his way, but Kuwabara wasn't part of his plan to fight Yusuke at his best, so outright killing the Spirit Sword wielder didn't interest him. Nonetheless, Kuwabara took the attack knowing Yusuke would be able to surpass his level at the time and allowed himself to "die" for his friend's sake.
When Kuwabara Cut Down the Demon World Barrier
After Yusuke is "killed" by Sensui, Kuwabara leads the retaliation by following the villain into Demon World. To do this, Kuwabara cut down the barrier between the Demon and Human worlds, knowing it would allow demons of all levels to pass through. He was willing to put Yu Yu Hakusho's entire world at risk to try and stop Sensui.
What Kuwabara couldn't have known was that the demon violence against humans was orchestrated by King Enma to keep Spirit World in control, which Koenma later found out. So there was little chance of any major catastrophe taking place by destroying the barrier. Of course, nobody knew that at the time and the barrier was temporarily rebuilt, but the entire Sensui conspiracy got the ball rolling.
When Kuwabara Refused to Fight For a Week
This may not seem as heroic as some of the other events in Yu Yu Hakusho, but it's actually one of the first instances we see of Kuwabara willing to take the fall for others. His friend Okubo works after school, which normally isn't allowed because students should focus on their schoolwork. However, Okubo is the only one in his household who can work, so a special exemption is made. When his job is threatened by the incorrigible Mr. Akashi, all of Kuwabara's gang swear not to fight for a week.
The promise is particularly hard for Kuwabara, who is now the toughest delinquent at the school and a prime target for other gangs. Despite how much he wants to fight back, he allows himself to be pummeled several times to ensure Okubo keeps his job. You can't ask for a better friend than that.