Joshua, along with Neku, Shiki, Beat, and Rhyme are the first characters to appear in the Kingdom Hearts series who originated from something other than Disney, Final Fantasy, or Kingdom Hearts fiction, although they are from another game that is property of Square Enix, as well as being designed by Tetsuya Nomura.
Joshua is a lanky, fair-skinned teenager with scraggly ash-blond hair and lavender-colored eyes. He wears a white button-down shirt, with a fairly exposed neck and collar. Joshua wears dark grey pants and plain white shoes with black laces. In a glimpse of his true nature, Joshua can manifest shining white, ethereal wings on his back.
In The World Ends With You, he is shown in his true form as the Composer on occasion. He is much taller in this form, and glows a pure white, making it hard to see whether he is wearing some type of angelic clothing or not. His hair is slightly longer, the ends of it resting along his shoulder.
Joshua is an extremely intelligent and mature character, with a refined taste and extensive knowledge of the world around him. He prefers to think and act by himself, always keeping his intentions mysterious, and is therefore difficult to predict. Joshua is shown to be a very cool-headed individual and rarely displays signs of distress as a result. When not sharing crucial information, he usually teases those around him in a lighthearted yet condescending manner. Unfortunately, his positive traits are often overshadowed by his constant air of arrogance, making Joshua seem aloof and antagonistic to others. Although he does not show it, Joshua is a very lonely individual, expressing reluctance to consider himself a friend, and establishing bonds with very few people, as shown when he explains to Sora how he doesn't have a special partner such as the players do with a sad expression.
In addition to his outward characteristics, Joshua is also shown to have a strong perception far beyond that of an ordinary person. He displays a deep understanding of the world around him, and is often shown explaining the workings of the universe and the worlds within. Joshua is a mysterious individual, usually shrugging off complicated questions and giving responses that provide no definitive answer. As a result, his comments often leave it up to the receiver to judge whether or not he is telling the truth. Joshua's deductive skills are so impressive, that he not only seems aware of the problems caused by Xehanort and the power of the Keyblade wielders, but even suspects that Sora and Riku's journeys through the Realm of Dreams are leading them into a trap, and helps Riku to understand how the worlds work. He also claims to be omniscient at least once, making it questionable sometimes whether or not Joshua is human.
 Kingdom Hearts 3D: Dream Drop Distance
Joshua meets Riku in the Third District of Traverse Town. He sits atop the arch over the fountain and tells Riku about the goings-on in town, asking for his assistance in locating a girl named Rhyme, whose dreams he has been using as a Portal to another version of the town. Riku refuses initially, but when Joshua implies that Sora might be on the other side of the Portal, Riku reluctantly agrees to help him out.
When Joshua and Riku reach the Second District, Riku asks why the Dream Eaters don't attack Joshua. Joshua answers that the Dream Eaters "only attack dreamers", and that for some unknown reason, even though Joshua has plenty of dreams, he apparently isn't one, as the Dream Eaters pay no attention to him. When Riku wonders if he himself is a dreamer, Joshua says that "all human beings are dreamers." At this point, Joshua gives Riku the Komory Bat Recipe to assist him in battle.
Just as Riku's new Spirit friend materializes, Beat charges into the District, shouting threats at Joshua due to someone telling him that taking Joshua down would result in him and Rhyme returning home. Joshua insists that Beat has been tricked by "that rogue in the black coat", a remark that immediately catches Riku's attention. Beat, having had it with Joshua's "reverse psychiatry", summons a Kooma Panda Dream Eater to battle Joshua and Riku. The Panda, however, is a Spirit, and ignores Joshua's presence completely, wanting rather to play around with Riku's Komory Bat. Several Nightmares appears, Riku dispatches them and Kooma Panda. Beat then relents, explaining that he would been willing to try anything to save Rhyme. While he doesn't notice himself, Joshua ignores Riku passing out, and neither is present when Riku wakes up again, as they are still in the other dreaming of Traverse Town.
After Sora defeats the Hockomonkey in the Fifth District, Joshua appears before him after saving Rhyme by using her as his portal between dream worlds, and explains that he and Riku are in two seperate versions of Traverse Town, as Sora sees an illusion of Riku and the unknown figure in the black coat that Joshua creates. Riku sees a similar image of Joshua, Sora, and Rhyme after he defeats his side's version of the Hockomonkey.
Later, Joshua speaks to Sora and Riku simultaneously, between the two sides of Traverse Town, being in between both dream worlds. He explains that when the original world of Neku, Shiki, Rhyme and Beat had vanished, he found Traverse Town using Rhyme's dreams as their new home. He also tells them that they are able to see each other is because of the strong bonds between, using Neku and Shiki and Beat and Rhyme as examples and says that Sora and Riku play a big part of making everything happen. When Sora and Riku ask in unison who he really is, Joshua simply chuckles softly and says, "Let's say... a friend." At those words, ethereal angel wings sprout onto his back, surprising the pair, and he flies up into the night sky and disappears.
On Sora and Riku's return trips to Traverse Town, Joshua coordinates between them in order to defeat the Spellican. During the event, Joshua confined in Riku that his earlier theory of the two Traverse Towns being parallel worlds is proven wrong as the timer on each one of reunited pairs is different from the other's partner. As Riku leaves after finishing his part in the plan, Joshua warns Riku to be on his guard as either of the journeys he and Sora are each on could be a trap, and that he may be traveling in a dream in a dream.
Yoshiya "Joshua" Kiryu is a character from Square Enix's The World Ends with You, being the overall antagonist of the story. A sly and precocious boy with an incredibly deep view of the world around him, Joshua is actually the god-like Composer of Shibuya. His role was originally to oversee the Reapers' Game, but decided to erase the district and everyone in it, accepting the challenge of Shibuya's Conductor, Megumi Kitaniji, to see if Shibuya deserves to be saved within three weeks of the Reaper Games. To that end, seeking a proxy to use against Kitaniji, Joshua arranged Neku Sakuraba's enrollment by personally killing him. Joshua partners with Neku in the beginning of the second Reaper's Game for various reasons, becoming an illegal player as he did not die to enter the game. During the week, Joshua looks for the "Shibuya River" with Neku, using a tracker Mr. Hanekoma installed in his and Neku's cellphones. By the end of the week, Joshua was seemingly killed off by the Reaper Sho Minamimoto. However, during the final battle with Kitaniji on the final day of the third Reaper Game, Joshua appears and reveals himself to be the Composer. Once Kitaniji is killed, instead of destroying Shibuya as he had won the bet, Joshua offers Neku a chance to determine Shibuya's fate: by killing him in a pistol duel. Though Neku lost as he refused to shoot, the total change of the boy's personality and trust in him convinced Joshua to spare Shibuya. In the end, while Neku and the others meet up, Joshua watched them from afar atop the 104 building before flying off.