Bason is the ghost of an ancient Chinese wujiang who serves Ren faithfully and obeys him without question. In the English manga Bason calls Ren "Master Ren," while in the Japanese version he calls Ren "Bocchama," which means "Young Master.
Bason is Ren Tao's spirit ally who serves the Tao family for many centuries. Bason rarely shows emotions and in the manga, his origin story is not shown in great detail like Amidamaru or Morphine. Like most spirits who get integrated into spirit mediums, Bason gets integrate into Ren's body, a spear, and a sword.
Bason, who is created by Hiroyuki Takei, has no current information on what inspires the author to create him. His Japanese voice actor is Shinichi Kotani, and his English voice actor is David Brimmer. He first appears in volume 1 and episode 3.
Bason has no evolution because he is a static character compared to Amidamaru and Tokagero, who have change their goals, when becoming Yoh and Bokuto no Ryu's spirit ally, respectively.
NOTE: These are not official arc names due to the lack of information from the author and notes in the manga.
NOTE: The information below is manga only info. See anime differences under "anime and manga differences" paragraph.
Bason makes his first appearance when Ren fights Yoh Asakura for the first time. Bason's master wants Yoh's spirit, and when Ren has the upper advantage due to his 100% integration, Yoh, who finally integrates with Amidamaru 100%, defeats Ren with Buddha Giri. After Ren's loss, Bason counters another enemy, Bokuto no Ryu and his gang. Ren blames Bason for letting them in, but Bason states that he is a ghost and people walk through him. Ren easily kicks Ryu out.
Bason assists Ren in killing Chrome, a Patch officiant, and Ren takes the oracle pager which makes Ren an official participant in the tournament. Bason makes another appearance as Ren's new oversoul when Ren uses to crush Faust's 20 ton calcium giant skeleton. During Ren's third preliminary match, Ren can make Bason materialize and rides a horse which has Bason's spirit integrate into it. However, Ren loses his temper which causes his will to waver. Yoh takes advantage of Ren's will and destroys Ren's oversoul twice that causes a huge loss of mana (or furyoko). In the end, Ren and Yoh's oversoul dissipates at the same time which ends up in a draw. Silva tells Ren and Yoh that they have won and can go on to the next round. At Yoh's house, Bason watches Ren make new friends, and he sheds his tears while he talks to Amidamaru that he is happy to see Ren happy.
Bason talks to Ren and Ren explains that he will end the cycle of vengeance by defeating his father, Tao Yuan. During the train ride, Bason witness Ren's change as he accepts a sweet bun from an old lady. Ren admits to Bason that not all humans are evil. After arriving back at home in China, Ren integrates Bason into the spear and attacks the welcome wagon of Jiang-Si outside of the tower. Tao Yuan makes his appearance and reveals the dismembered Pailong, and Jun Tao, who is in chains, is held captive by the Torture Brothers. When Ren is held captive, Bason begs Yoh and friends to save Ren Tao and his sister from Tao Yuan. (See vol. 8 and 9)
Bason accompanies Yoh and friends and he watches Ren's growth after this arc. Bason acts like a guide for Yoh and friends when he points out that the Curse Squad is tricky and dangerous. After Yoh rescues Ren, Ren and Bason sees the leader, Sha Wen, of the Curse Squad holding Ryu by the throat. Sha Wen easily overcomes Yoh and Ren with his Do Dan Do. When Sha Wen is about to thrust his palm in Yoh, Pailong stops Sha Wen. Bason and Ren observe's Sha Wen's defeat when Pailong crushes Sha Wen's corpse. Bason accompanies Ren and Yoh's team when they confront Tao Yuan. After Ryu and Horohoro's failed attempt to hurt Tao Yuan, Ren integrates Bason and attacks his father. During the battle, Ren figures out that they are actually fighting his father's oversoul, and Ren defeats his father's dragon oversoul because his father's will wavers which causes Tao's oversoul to become weaker. Ren's grandpa and mother stop the battle, and invites everyone to dinner. After dinner, Bason accompanies Ren who rides his horse to Tokyo. Tao Yuan, who is riding his dragon oversoul, gives Ren his treasured sword, Jewel Thunder.
Bason meets Hao Asakura, Hao's followers, Lilirara, Lyserg, X-laws, and the Great Spirit on his journey. When Hao makes his first appearance to Yoh and the others, his spirit of fire attacks Horohoro due to his insult. Ren attacks Hao immediately, but Hao knocks him down. Hao states that he wants Yoh to join him after he gets stronger. After climbing aboard the Patch's jumbo airline, the Patch announces their true intentions. The Patch's rules states that participants must reach the Patch village in three months or be disqualified. With that rule, the Patch dematerializes their oversoul which is the plane, and every shaman drops from the skies. After Yoh and the gang focus their oversoul on the ground at the same time, they hitchhike on Billy Anderson's trunk and head to Yonte Fe. At Yonte Fe, Bason meets Lilirara. After Bason's master finds out more about the "Patch" Hao, Yoh's team heads out to Mesa Verdede. On the way, Bason and Ren encounters Lyserg and Morphine. Lyserg, whose parents is murder by Hao Asakura, challenges Horohoro and Ren to prove himself. After Lyserg injures Ren and Horohoro, Yoh defeats Lyserg. At the hospital, Lyserg joins Yoh's team after he agrees to pay for the weapon repairs and hospital bills.
At Mesa Verdede, Bason and Ren meets Hao's followers, Big Guy Bill, Boris, Damayji, Mohamed, and Zang Hang. They are under orders to kill Yoh's teammates, and Boris Tepes Dracula attacks Lyserg. After Boris's spirit ally, Blamuro, controls Lyserg, Blamuro forces Lyserg to hold Yoh and his harusame pointed at Lyserg's throat. At the same time, Ryu, Horohoro, and Ren have stakes (made of tourist's blood) waiting to drop on him. Although Boris has Yoh's team in a tight situation, Ren and Bason destroys Boris's stakes while Amidamaru helps Blamuro stop obeying Boris's orders. After taking control of the situation, Ryu attacks Boris with all of his might. The X-Laws make their first appearance when Marco's arch angel, Michael, kills Boris. In the caves with Yoh's team following the X-Laws, Bason asks Ren that arch angels are myths and they cannot exist. When Big Guy Bill attacks X-Laws, the X-Laws defeat him easily. After Yoh attempts to stop Marco from killing Big Guy Bill, Yoh's Harusame breaks.
Bason's first match is the first match of the tournament when his team, Team Ren, fights Team Tsuchi Gumi (Earth). After Chocolove defeats BoZ and uses Oversoul, Gag Wind, that weakens Peyote Diaz's control over his spirt medium, Ren uses his oversoul and materializes Bason to deliver a solid punch on Peyote. Ren knocks out Peyote Diaz out of bounds. (see vol. 14)
After Yoh's match with Team Ice Men ends, Bason sees Hao Asakura trying to recruit Ren. Hao makes an offer to Bason's master that if he joins him, Hao will teach Ren a better Ultra Senji Ryakketsu. Ren, who is stubborn, declines Hao's offer because Ren states that he will get strong his way. Hao mocks Ren by telling him that he cannot defeat Yoh and Hao which prompts Ren to strike at Hao with his spear. Hao instantly burns Ren's spear.
During team X-III's match with Hao. Bason and Ren watch the massacre of team X-III at the hands of Hao. Ren figures out Hao's spirit medium which is the air (more specifically oxygen).
Bason and Ren fights Mikihisa Asakura and learns the ways of the Ultra Senji Ryakketsu. Ren easily dodges and counters Peyote Diaz, Mohamed, and Hang Zang. However, when Nichrom mentions his brother, Chrom, is a weakling, Ren is caught off guard and gets impale by Peyote's Fantasma Grande.
Ren can reach 100% integration with Bason and uses all of his techniques.
According to Hao Asakura, Ren's mana is 5,721 which is reported after Ren's match with Peyote.
Note: In the anime, characters meet characters early or later their original manga counterparts.
Unlike the manga, Bason encounters Ryu in a cemetery.
Unlike the manga, Bason fights Amidamaru twice before the third preliminary match. First battle is Ren's victory and the second battle is Yoh's victory.