Yu Yu Hakusho protagonist Yusuke Urameshi and his comrades are forced to compete at the Dark Tournament by the Toguro brothers, but they're not just facing bloodthirsty fighting opponents. They also face several instances of cheating from the other teams' owners and the Tournament committee who want to see Yusuke dead. One of the most blatantly corrupt decisions comes in the third round as Team Urameshi faces the mysterious ninja quintet Team Masho... and Team Urameshi needs a major ally to save them all.
Yukina, an ice apparition who was previously rescued from captivity by Yusuke and Kuwabara, tries to get into the Tournament stadium to cheer them on but has no tickets. Her arrival comes at a vital point, with the heavily injured Kuwabara forced to fight the third round's deciding match and getting pummeled in the process. Yukina's appearance not only inspires Kuwabara to victory but saves everyone from what would've been certain death in the final round against Team Toguro.
The cheating from Team Masho's owner begins right at the third round's start. A "nurse" is suddenly introduced and declares Hiei and Genkai unhealthy and ineligible to fight. Yet Kuwabara is left alone despite lying on the ground with several broken bones from his second-round match. This leaves only Kurama and a battle-worn Yusuke left to face five fully healthy and highly skilled ninjas. Kurama's inspired intellect and noble sacrifice combined with Yusuke's brand new Spirit Wave technique defeat four of their opponents. However, Yusuke's second match is ruled a double loss after both stay outside the ring for longer than the allotted 10 seconds.
As Yusuke and Kurama have both technically lost a fight, while Hiei and the masked Genkai are already ineligible, the badly injured Kuwabara stumbles into the ring to fight the shinobi leader Risho. Kuwabara is getting massacred and decides to tap into his Life Energy, effectively sacrificing his life to kill Risho as well so the rest of Team Urameshi can advance. But just as he's doing so, he spots Yukina who finally got into the stadium thanks to Botan. Kuwabara's power is much like Yusuke's, only coming out when his deepest feelings and emotions are brought to the surface. Revitalized by seeing the love of his life, Kuwabara's energy returns and he defeats Risho with his Spirit Sword.
Yukina's appearance not only directly aided Team Urameshi through the third round but was also crucial for two more reasons. First, there's no guarantee Kuwabara's sacrificial move would've killed Risho. Each member of Team Masho is a master of a specific elemental art, and Risho's specialty is Earth. His most powerful moves are defensive, creating powerful armor for protection. And as Risho was aware of Kuwabara's plan, it was a massive gamble to take.
Second, the Dark Tournament's final round requires both teams to have five members. Genkai was killed by Younger Toguro outside the stadium, leaving only Yusuke, Hiei, Kurama and Kuwabara left. Koenma (Team Urameshi's owner) steps in as the fifth member despite not being a physically skilled fighter. But if Kuwabara hadn't stopped his suicidal attack upon seeing Yukina, Team Urameshi would've been left with just three fighters and Koenma, leaving them unable to compete. Elder Toguro had explicitly stated that his wish -- one given to each member of the Tournament's winning team -- would be the deaths of Team Urameshi and all their friends.
Yukina is best known and loved for her kind heart and impressive healing abilities, but for Kuwabara and Team Urameshi's journey through the Dark Tournament, her very presence was crucial in keeping them all alive.
