[url=https://www.youtube.com/watch?v=9XmtN4Gt8C8]Handy video guide to understand Double's powers.[/url] Two characters counted as one.

[hider=Double's Left Side: Shotaro Hidari][list]
[*][b]Name:[/b] Shotaro Hidari
[*][b]Age:[/b] Early 20’s
[*][b]Gender:[/b] Male
[*][b]Appearance:[/b] [url=http://i.imgur.com/IpuDOxp.jpg]Civilian form[/url], [url=http://vignette3.wikia.nocookie.net/kamenrider/images/c/cf/KRW-Joker.png/revision/latest?cb=20140528140643]Solo Joker form.[/url]
[*][b]World of Origin:[/b] [i]Kamen Rider W[/i]
[*][b]Personality:[/b] A tough and cynical man… One who’s cool under pressure and always gets his man… [i]A hardboiled detective[/i]… That is not what Shotaro Hidari is. He’s more accurately a [i]half[/i]boiled detective if anything. Shotaro typically tries to act like a serious and cool-looking guy, but it’s very easy to poke fun at him and break that facade to reveal how emotional he really is. When it comes to his friends and clients, however, he’s 100% serious for them if they’re in any kind of trouble. If you make them cry, he’s more than willing to return the favor.
[*][b]History:[/b] Shotaro was born and raised in the windy city of Futo. He has a great fondness for the city and has vowed to protect it from anyone who would make it (and its residents) cry. In his aspirations to become a hardboiled detective, he became an apprentice under Sokichi Narumi, an [i]actual[/i] hardboiled detective. One night the two investigated a building researching Gaia Memories and rescued a mysterious young man Sokichi named Philip. On that same night, Shotaro’s inexperienced recklessness caused Sokichi to be killed. To atone for it (and also to escape the building), he joined with Philip to become the two-in-one Kamen Rider Double. Together, the two fought against this organization and eventually put an end to it.
[*][b]Abilities:[/b][list]
[*][i]Ace Detective:[/i] His detective training had to pay off eventually. Shotaro is a very competent private detective with a keen eye for detail and deductive intuition.
[*][i]Kamen Rider Double:[/i] Using a belt called the [i][url=http://ecx.images-amazon.com/images/I/61t3HubVk8L._SX522_.jpg]Double Driver[/url],[/i] Shotaro can link his and Philip’s consciousness. Taking it further, using Gaia Memories with it will let Philip’s consciousness enter Shotaro’s and cause them to transform into a Kamen Rider.
[*][i]Kamen Rider Joker:[/i] Using a belt called the [i][url=http://image.rakuten.co.jp/auc-rebirth/cabinet/04301439/imgrc0080052411.jpg]Lost Driver[/url][/i], Shotaro can use a single Gaia Memory to transform into a Kamen Rider by himself.
[*][i]Gaia Memories:[/i] Shotaro’s Gaia Memories affect Double’s left side and affect its physical capabilities They are also usable in his own Lost Driver.[list]
[*][i][url=http://vignette1.wikia.nocookie.net/kamenrider/images/5/52/Joker_Memory.jpg/revision/latest/scale-to-width-down/78?cb=20150211232055]Joker:[/url][/i] Shotaro’s default Memory. Greatly improves their hand-to-hand fighting ability.
[*][i][url=http://vignette4.wikia.nocookie.net/kamenrider/images/2/24/Metal-Memory.jpg/revision/latest/scale-to-width-down/57?cb=20150211232055]Metal:[/url][/i] Greatly improves their strength and resilience to physical harm. Gives them the [i][url=http://img.amiami.jp/images/product/review/101/TOY-TOK-0773_04.jpg]Metal Shaft[/url][/i] for a weapon.
[*][i][url=http://vignette4.wikia.nocookie.net/kamenrider/images/1/1a/Trigger_Memory.jpg/revision/latest/scale-to-width-down/70?cb=20150211232056]Trigger:[/url][/i] Greatly improves their marksmanship and equips them with the [i][url=http://img.amiami.jp/images/product/review/101//TOY-TOK-0882_08.jpg]Trigger Magnum[/url].[/i]
[/list][/list]
[*][b]Other:[/b] Shotaro’s phone, watch, and camera actually have Gaia Memory utility too, but this is getting long so I’m just gonna have them not use it.
[/list][/hider]
[hider=Double’s Right Side: Philip][list]
[*][b]Name:[/b] Philip
[*][b]Age:[/b] 17
[*][b]Gender:[/b] Male
[*][b]Appearance:[/b] [url=http://www.cosplayisland.co.uk/files/costumes/233/37963/philip.jpg]Civilian form[/url], [url=http://vignette2.wikia.nocookie.net/kamenrider/images/7/77/KR-CycloneJoker.png/revision/latest?cb=20150225063116]Double form.[/url]
[*][b]World of Origin:[/b] [i]Kamen Rider W[/i]
[*][b]Personality:[/b] Philip is the logic to Shotaro’s heart, and the brains to his brawn. He approaches matters from a calmer standpoint than Shotaro, but should his friends ever find themselves in trouble he can easily get as riled up as him. When it comes to researching something interesting, Philip can have a bit of a one track mind. He can suddenly spend days at a time researching a topic without break if he can help it, and is known to go to extremes to better understand it. Once he’s learned all there is, he can just as suddenly drop interest in it entirely.
[*][b]History:[/b] When he first met Shotaro, Philip had no memory of his past and simply worked in the research building Sokichi and Shotaro broke into. He’s considered a highly valuable person to the organization he belonged to, and subsequently had to spend most of his time out of sight in the detective agency. As he and Shotaro defended Futo as Kamen Rider, he gradually came out of his shell and built a strong bond with Shotaro, his friends, and the city. They also learned the truth behind his past and his connection to the Gaia Library.
[*][b]Abilities:[/b][list]
[*][i]Gaia Library:[/i] Philip has a connection to the Earth itself, and can call upon its memories to learn anything he wants. Of course, this doesn’t mean he learns things in a snap. The library manifests itself as a literal library and requires keywords to find what he’s specifically looking for. Limited only to what his Earth knows.
[*][i]Kamen Rider Double:[/i] When Shotaro puts on the Double Driver, a second will manifest on Philip’s body. While it’s mostly Shotaro doing the transforming, Philip can take the reins as well if Shotaro puts a Memory in first instead of him.
[*][i]Gaia Memories:[/i] Philip’s Gaia Memories affect Double’s right side and give it different effects.[list]
[*][i][url=http://vignette3.wikia.nocookie.net/kamenrider/images/f/f9/Cyclone-Memory.jpg/revision/latest/scale-to-width-down/78?cb=20150211232054]Cyclone:[/url][/i] Philip’s default Memory. Adds windy effects to Double’s attacks.
[*][i][url=http://vignette1.wikia.nocookie.net/kamenrider/images/0/00/Heat_Memory.jpg/revision/latest/scale-to-width-down/65?cb=20150211232055]Heat:[/url][/i] Adds fiery effects to Double’s attacks.
[*][i][url=http://vignette3.wikia.nocookie.net/kamenrider/images/d/dd/Luna_Memory.jpg/revision/latest/scale-to-width-down/65?cb=20150211232056]Luna:[/url][/i] The “illusions” Memory. Allow’s Double to stretch their limbs or bend their weapons. 
[*][i][url=http://vignette2.wikia.nocookie.net/kamenrider/images/d/d3/Fang_Memory_-_Live_Mode.jpg/revision/latest/scale-to-width-down/185?cb=20130730232846]Fa[/url][url=http://vignette1.wikia.nocookie.net/kamenrider/images/3/3a/Fang_Memory_-_Memory_Mode.jpg/revision/latest/scale-to-width-down/185?cb=20130730232906]ng:[/url][/i] A sentient Memory that serves to protect Philip. Using it has Philip take the reins to become the berserker-styled fighter FangJoker.
[*][i][url=http://vignette2.wikia.nocookie.net/kamenrider/images/a/a5/Xtreme_Memory_Live_Mode.jpg/revision/latest/scale-to-width-down/185?cb=20130730234414]X[/url][url=http://vignette2.wikia.nocookie.net/kamenrider/images/1/18/Xtreme_Memory_Memory_Mode.jpg/revision/latest/scale-to-width-down/185?cb=20130730234438]treme:[/url][/i] Double’s strongest memory. It’s also sentient and flies to Double on Shotaro or Philip’s command. It can turn Philip into data so that he and Shotaro can become one. Turns Double into [url=http://3.bp.blogspot.com/_YF1tNfQVN8w/S7NKh8FegVI/AAAAAAAAsv4/L6Jd3Bi8k4I/s1600/6.jpg]CycloneJokerXtreme[/url] and arms them with the [url=http://vignette1.wikia.nocookie.net/kamenrider/images/f/fb/Prism.jpg/revision/latest?cb=20140224085949]Prism Bicker[/url]. The Prism Bicker can store four Gaia Memories (three of Philips, one of Shotaro’s) to charge energy up for a finishing move. Transforming into Xtreme can potentially undo negative mental effects on either Shotaro or Philip. [b]Limited to one use per world.[/b][/list][/list]
[*][b]Other:[/b] CycloneJokerXtreme can actually go EVEN FURTHER BEYOND if it gets hit by a lot of wind. It only gives them wings, though, and it never actually shows up in the series, so I’m fine with omitting it.
[/list][/hider]