|Also known by its English adaptation title, "The Substitute" arc, the first Bleach story arc is twenty episodes in length, and initially aired in Japan from October 2004 through February 2005.|
Ichigo Kurosaki is a 15 year old teenanger with an unwanted talent for seeing ghosts. This talent allows him to spot the shinigami Rukia Kuchiki, whom he inadvertently interferes with during her duties. When Rukia is injured by a hollow that attacks Ichigo's home, Ichigo is forced to temporarily take her shinigami powers to defeat the hollow. The next day, Rukia shows up at Ichigo's school as a normal human. She tells him that she has lost all of her powers, rather than merely the fraction she intended to give him, and cannot carry out her duties. Ichigo must take her place as Karakura Town's shinigami while she recovers, guiding souls to the afterlife and defending people from attacking hollows.
Ichigo's spiritual power as a shinigami is surprisingly large, attracting hungry hollows and even affecting nearby humans by awakening any spiritual powers they possess. His powers also attract an enemy of another type: Uryū Ishida, one of the few remaining Quincy, a race of spiritually-empowered humans who were butchered by the shinigami long ago. In order to prove the Quincy are better than shinigami, he challenges Ichigo to a hollow hunting contest. This goes horribly awry, as the bait Uryū uses to start the contest is far more effective than intended, summoning legions of hollows. During this contest, Yasutora "Chad" Sado and Orihime Inoue, two of Ichigo's friends, have their own spiritual abilities awakened when they are assaulted by hollows. Uryū and Ichigo eventually ally to drive off the hollows.
As the remainder of the school year passes, Ichigo, Rukia, Chad, Orihime, and Uryū become close friends. Rukia begins to grow comfortable with life in the living world but realizes that she needs to leave. Having already spent too much time in the living world without permission, she has become a wanted criminal. Her superiors in Soul Society send two elite shinigami, Renji Abarai and Byakuya Kuchiki, to arrest her. Ichigo tries to prevent the arrest, but his efforts are in vain. Not only is he defeated, but Byakuya strips him of the shinigami powers Rukia had given him. Rukia is taken to Soul Society, where she is put on death row.
Kisuke Urahara, a mysterious shopkeeper and ex-Soul Society resident, approaches Ichigo with a way to recover his powers and save Rukia: Ichigo must die, and then find the shinigami powers hidden within his own soul before he becomes a hollow. Ichigo narrowly succeeds in this endeavor, but emerges from the training stronger than he ever was before. Ichigo, Chad, Orihime, and Uryū then set off for Soul Society, led by one of Urahara's friends, a seemingly male talking cat named Yoruichi.