The Mod Soul Incident

The Mod-Soul Incident is an event during the Agent of the Shinigami arc which introduces the use of a Mod-Soul named Kon as a means to separate Ichigo's soul from his body.

Prelude
After spending several months in the Human World, Rukia realizes it won't be long before someone of the Gotei 13 would come after her. She also realizes after all that time she hasn't regained any of her former powers. She decides to find a method for Ichigo to separate his soul from his body unaided. She goes to the Urahara Shop and, using the credit she earned killing Shrieker, she purchases what she believes to be a dispenser of soul candy. When she meets Ichigo in school, she pulls him to an empty yard and forces him to take one of the pills. Once Ichigo's soul separates from his body, his body falls under the control of what appears to be an Artificial soul. Ichigo has reservations about the Artificial soul's behavior but Rukia receives an order on her soul phone and drags Ichigo away, leaving the Artificial soul within Ichigo's body to his own devices. Back at the Urahara Shop Urahara discovers an open carton in storage that should have remained closed.

School Daze
At the Urahara Shop Ururu is confronted by her mistake: She delivered a faulty piece of merchandise to a customer. Tessai and Urahara realize that once the item delivered to Rukia would gain a Human body, it would cause trouble for sure. At the school, the being inside Ichigo's body begins to test his newly acquired body. He kicks in a piece of railing, destroying it effortlessly, but is caught red handed by a teacher, who recognizes Ichigo. Without saying a word, the Artificial soul advances on the teacher but at the last moment jumps over his head and lands on a rooftop twenty yards away, leaving the teacher stunned.

Over at Ichigo's classroom the girls are getting ready to eat their lunch, which is, as Orihime says, the only reason teenage girls go to school. Tatsuki and Chizuru get into their usual fight about Orihime when she suddenly gets up from her lunch and walks to the window, having smelled Ichigo, as she says. Tatsuki begins to say Ichigo won't come in through a third story window but then the Artificial soul jumps up to the window from the ground, three stories down, causing a real uproar among the girls in the room. The Artificial soul is quite pleased with the attention he is receiving, and is most impressed with the looks of the girls in the class, that is until he notices Orihime and her large chest and makes a move on her. When Tatsuki tries to pull him off he turns his attention to her and notices that she too is quite cute from up close. The Artificial soul gives Tatsuki a kiss on the cheek.

When Ichigo and Rukia return to the school, after defeating the Hollow, they find school desks flying out of the window of their classroom and Rukia is forced to admit that something might be off. The desks are thrown by Tatsuki and aimed at who she believes to be Ichigo, but he still manages to dodge her attacks. Rukia arrives at the classroom door and blocks the Artificial soul's escape route. Ichigo tries to block the window, but the Artificial soul manages to jump past him and run away. Rukia finds it hard to believe, but says there is no doubt the being in control of Ichigo's body is not an Artificial soul but a Mod-soul.