Modified souls are artificial souls created by Soul Society researchers some time ago. They have enhanced speed and strength when compared to normal humans, and often special abilities which set them apart from each other. However, the modified souls were considered an unethical experiment and most of them were destroyed. Urahara saved at least one of them, Kon (コン, Kon?).
Kon
Kon primarily serves as a comedic foil in the series; when not inhabiting Ichigo's body, his normal plushie body is treated with little respect and much disdain. The humorously cruel treatment he is always subjected to provides the comic relief in Bleach. One of the only people who gives him any respect is Chad; however, Chad ignores him most of the time. His plushie body is a knock-off of the main character of the popular TV show Carnivore Kingdom, named "Ponkichi", which happens to be Chad's favorite show. It was a prize from the shooting game in the Karakura Town Festival.[2] He is constantly stepped on and torn, at which point Ichigo will have Uryū Ishida repair the plushie. Uryū usually adds something unwanted or unnecessary when doing so, such as dressing Kon up like a designer doll. Uryū also sewed a Quincy cross on the back of Kon's head as revenge after Kon attacked Uryū for turning him into a doll.
Kon is quite perverted and often takes advantage of his form to get girls to hug him to their chest, which rarely goes as planned. After Ichigo becomes less dependent on Kon to transform, Kon comments on how he wouldn't mind taking Ichigo's body out for a spin again, saying that he'd like go pulling up skirts because, as he puts it, "It's Ichigo's reputation that gets sullied". Kon is very fond of Rukia, calling her "sister", though this extends to basically any pretty girl.
Kon also serves as the host of various omake segments in the anime, which are shown after the ending credits of each episode beginning with the Soul Society arc. The first, called the "Shinigami Illustrated Picture Book", has Kon introducing various shinigami by name and rank, followed by a short one-liner about them. These segments run from episodes 14 to 49, after which there is a four-episode break. Starting with episode 54, the ending segment is renamed "Shinigami Illustrated Picture Book: Golden", which shows comical situations with the series characters. Kon does not host these, though he is featured prominently in quite a few, but rather is part of the screen wipe that opens into them. A sub-group of these sketches, running from episode 119 to 124, is called "Kon-sama's Erotic Conquest of Soul Society", where Kon takes over Hanatarō Yamada's gigai in order to move about Soul Society, only to find that his choice is less than helpful for his intended goals.
Kon's first appearance is shortly after Rukia Kuchiki and Ichigo obtain an item known as gikongan (Soul Candy) from the Urahara Shop, which are candy-like orbs stored in dispensers similar to those PEZ come in. The Soul Candy, when ingested, forces Ichigo's soul out of his body and replaces it with an artificial, pre-programmed soul, allowing Ichigo to transform if Rukia is not around. Unbeknownst to everyone (including the Urahara Shop's employees), the particular Soul Candy dispenser Urahara gives Rukia had been declared defective by Soul Society, as it was made from a batch meant to be turned in for destruction. These pills contained modsouls, artificially created souls designed to combat hollows. Additionally, these souls have personalities, unlike the common artificial souls. Each modified soul was designed to have their own special strengths; in Kon's case, his legs. Upon first testing the item, Ichigo and Rukia leave it to its own devices while they go to fight a hollow.
The modsoul, now free and having no desire to return to its pill form, goes on a mischievous and damaging (to Ichigo's reputation) rampage, diverting Ichigo from the pursuit of a particularly dangerous hollow. The pair clash a few times during the course of the modsoul's spree, and would have continued had not the hollow chosen to appear and attack a group of children nearby. The modsoul acts on its instincts, attacking the hollow and giving Ichigo the time to defeat it. Afterwards, Ichigo has a talk with the modsoul, who explains that he just wants to be free and experience life, similar to that of a real soul. Taking pity on him, Rukia and Ichigo ignore the standing directive to destroy all modsouls; they instead stick the modsoul into a lion plushie that they find on the side of the road, giving it life. Ichigo gives the modsoul the name of Kon shortly thereafter, despite Kon's protests.
Noba, Kuroud, and Ririn with their creator Kisuke UraharaIn the anime's Bount arc, three more modified souls are introduced. Created by Kisuke Urahara, they are designed to track and combat the Bount, as well as help train Ichigo and his companions, although at first they're seen as a threat while doing so. They originally live in gigai created by Urahara, and have the ability to sense the spiritual presence of the Bount. However, early in the Bount arc, Kisuke asks the trio to primarily remain in plush doll bodies like Kon to remain inconspicuous.
As modsouls the three possess special abilities, but their abilities involve altering reality rather than physical enhancements. They change from plush animal to human gigais frequently when they need to fight, because their powers are in a very limited state when in their plushie bodies.
The following modsouls only appear in the anime. The story following the return to the manga plot has been slightly altered to accommodate their presence without changing the overall course of events. During an Arrancar Invasion, their gigai's are severely damaged. They comment at the end of one episode that they wanted to accompany Ichigo and the others to Hueco Mundo, but couldn't. Ririn and Kuroud then mention that they will obtain new, "sexy" gigai's much to Noba's disdain.[8]
Ririn
Ririn, while in her gigai form, is a small girl with short blonde hair wearing a pink, fur-trimmed coat, a purple bird-shaped cape, and red boots. When not in her gigai', she inhabits an anthropomorphic bird plushie. Her special ability is the creation of illusions. She acts as the leader of the trio, and has a fondness for games. She is partnered with Ichigo Kurosaki. At first she disliked Ichigo due to their conflicting personalities, but now she has grown to be very fond of him, even becoming at times extremely jealous of Rukia Kuchiki's close relationship with Ichigo. She can be petty and arrogant at times, but she shows real concern for her friends. She often looks down on Kon as inferior, which causes frequent arguments between the two.
Kuroud 
Also known as Claude or Cloud, Kuroud is a bespectacled man with a mustache and two-tone hair color (black to the right, yellow to the left). He wears a gray top hat, multi-colored suit and tie, as well as dark brown boots, giving him an appearance similar to a circus manager. His plushie body is a rabbit-esque purse. He is partnered with Orihime Inoue. He has the ability to shapeshift, and can replicate the abilities of others when he does so (although he can't replicate the power levels of said abilities). He is somewhat cowardly and is terrified of snakes. His longwindedness and actions often provide comic relief. He is also somewhat perverted, like Kon, or at the very least is thankful for the opportunity to be held by attractive women (being a purse helps in this regard). Rukia seems to like him because he resembles Chappy the Rabbit in his stuffed animal form.
Noba 
More commonly known as Nova, Noba is a handsome young man in a fur coat with a shield on his back and a zippered mask, with a slim build, red hair, and aqua eyes. He inhabits an anthropomorphic turtle plushie in grey dress trousers and a white ruffled shirt with a red bow tie when out of his gigai. He's very quiet, rarely speaking more than a few words and also rather shy, zipping up his hood when he wishes to show emotion, in his gigai or pulling his head into his shirt in his stuffed animal form. He is partnered with Yasutora Sado, who is equally quiet. He has the power to teleport himself and others to most any location he's been to. He can also use his spiritual sense to teleport to the location of those with spiritual powers. Additionally, he can create wormholes to redirect ranged attacks, both physical and energy based, back at the enemy. He can also absorb fire. When he is in his plushie, his teleportation range is limited to about two meters.
