Daiki Kaito

Kamen Rider Diend (仮面ライダーディエンド) is one of the fictional characters and secondary Kamen Rider in the Kamen Rider Series of Kamen Rider Decade. His name comes from the English words "die" and "end", as well as "the end".

Personality
Daiki Kaito (海東 大樹, Kaitō Daiki) is a mysterious young man who is portrayed as being cheerful to the extent of being annoying to those around him, but becomes serious in battle and sees material objects as more important than anything else. Narutaki, aware that Daiki is Diend, avoids getting in his way. He also appears to know about Tsukasa's past, referring to sea cucumbers as being something Tsukasa had always wanted to taste. He travels from A.R. World to A.R. World, stealing what he refers to as "treasures". Daiki's surname is a homophone of the Japanese word kaitō (怪盗?, phantom thief), a role he fulfills in Decade.

It is revealed that he comes from an A.R. World (referred to as the "World of Diend") where he was an officer who served the evil Fourteen who has deemed Kamen Riders as threats to the public peace. Daiki hunted them down and turned them in for education until he captured the leader of the Kamen Riders: Kamen Rider Glaive. When Glaive is unmasked, he is revealed to be Daiki's older brother Junichi.

By then, Daiki learns the truth that Fourteen brainwashes people, powerless to stop him. Losing his self-confidence and seeking to undo all of the mistakes he had caused, Daiki stole the Diendriver from Dai-Shocker, becoming Kamen Rider Diend and becomes Fourteen's new most wanted Kamen Rider.

He leaves his world, traveling to other worlds and taking their treasures as a means of self-delusion until he crosses paths with Kamen Rider Decade. Eventually, he does lackadaisically accept the Hikari Studio residents as "friends", even calling Decade a "comrade", though he is not beyond abandoning them without explanation, usually for his own self-interest.

History
Though he briefly appeared in Blade's World, revealing he knows Tsukasa, Daiki found nothing worth taking. Arriving in Faiz's World ahead of Tsukasa, Daiki witnesses Faiz's battle with the Butterfly Orphnoch and was unable to catch him to acquire his Faiz Gear. When Tsukasa arrives in Faiz's World, Daiki reveals that Faiz is among the student body and warns him not to meddle in his affairs. However, as Tsukasa decides to find Faiz, Daiki gets Lucky Clover's aid by showing them the photograph that Faiz dropped during the fight under the assumption he wanted to join their group, leaving them to attack Yuri before Takumi becomes Faiz to protect her. Daiki then attempts to run away from school, but realizes that he needs to stay and make sure the belt is in proper hands.

When the Orphnochs acquire the belt, Daiki reveals his true intentions as he becomes Diend. He kills the Centipede Orphnoch before he and Decade fight over the Faiz Gear until Takumi regains it, later disposing of it. But in spite of being told Takumi had something more precious than the Faiz Gear, Daiki takes the Ride Booker from Tsukasa in an attempt to take the Faiz Gear from him. Narutaki whisks Tsukasa away to fight Kamen Rider Ryuga, but Daiki interrogates Kivala on the location to save Tsukasa, claiming that the Faiz Gear is what he came for as he gives Tsukasa back his Ride Booker.

However, during the Lucky Clover invasion of the Smart Brain School, Daiki returns once again to Tsukasa and Takumi's aid, returning the Faiz Belt to Takumi. After the fight, Daiki claims the Orga Gear for himself out of rubble while seeing it as the "more precious treasure" Tsukasa spoke of, leaving a little note on the painting of Agito's World as a warning not to meddle in his affairs again, which further irritates Tsukasa.

In Agito's World, Daiki is training along with Yuusuke and others to become the next G3-X user. Acquiring the position, it is only revealed later that Daiki's real goal in Agito's World is to steal the newly-created G4 chip that was stored in Ashikawa's locker, Yuusuke confronts him until Toko arrives and blasts the chip to bits. Daiki later aided Yuusuke in protecting Ashikawa, only to find out what he possessed to be more precious than the G4 Chip. However, seeing that to be his Agito powers, Diend leaves the fight scene to the next world as he could not take it with him.

In Den-O's World, Kaito attempts to coax the Imagin Momotaros, who took Yuusuke's body, into allowing him to use a Final FormRide card on him to become a DenLiner. When M-Yuusuke refuses, he is runned ragged by Diend until he leaves him to reconsider his offer.

However, when he offered again, Decade takes the card from Diend while defending Momotaros before helping him regain his self and form. Sticking around Den-O's World, Diend sneaks aboard the DenLiner to the past where his summoned Riders were used by Urataros, Kintaros, and Ryutaros.

In Kabuto's World, interested in the Clock Up ability of the Kamen Riders, Diend saves Decade from TheBee and Gatack, fighting the latter by himself as he is further impressed by the Clock Up System and proceeds to get it from Kabuto. But after the attempt blew up in his face, Daiki receives a "treasure" from Tsukasa which was actually a vial of pepper.

In Hibiki's World, after an attempt to rob Hibiki, Daiki learns from Asumu of the three scrolls owned by the three Oni schools. Working his way in Zanki's school, he makes a preposition to aid him in settling things with Ibuki and his school.

However, during the fight with Decade, Diend reveals his true colors after stealing the Zanki and Ibuki school scrolls and having Momotaros cover his escape. He then admits to get the last scroll from Hibiki who blocks his path and gives him his Onkaku to give to Asumu along with his final request. The next day, Daiki uses Asumu to distract Hibiki lost enough to steal the scroll, invoking the man's change into Gyuki to cover his escape. However, after reading the scrolls, Daiki returns to give Asumu the Onkaku in order to see the harmony of the three Ongekidō styles. He takes his leave soon after, though thanked by Asumu and the others in spite of his protest that his motives were selfish.

He is seen again in the Negative World, following Tsukasa before he overheard Otoya speaking of treasure that attracts the thief into fighting alongside Decade against the Dark Riders. Though he gained the treasure (through the use of paper airplanes), the K-Touch, Diend loses it during the fight.

Returning to the his home world Daiki meets up with his old friends Haruka and Shin as they fight Darkroaches as Larc and Lance, the latter blaming him for Junichi's brainwashing. Tsukasa approaches Daiki after Natsumi and Yuusuke have also been brainwashed by the evil Fourteen, and Daiki agrees to help Tsukasa, Haruka, and Shin defeat Fourteen and his brother who can transform into Glaive. Together, they reveal Fourteen's true form as Jashin 14 and destroy him, freeing everyone from brainwashing. However, Junichi revealed he was never under Fourteen's control and was working for him on his own free will. Diend and Glaive fight, though neither has the will to kill the other, especially after Tsukasa tells them that brothers must look after each other, no matter what.

Junichi and Daiki go their separate ways as Daiki travels to the next world, with the intent to obtain the Shinkengers' Origami. Starting with Genta Umemori's Ika Origami, Daiki runs off with Genta in pursuit. Deciding to fight him as he cannot lose him, Daiki gets an unexpected visit from Chinomanako who steals his Diendriver and hounds him until he makes his way to Tsukasa who has Yuusuke take him back to the Hikari Studio. He eventually gets it back from ShinkenGold when Chinomanako is destroyed by the combination of Decade, Kuuga, and the Shinkengers in exchange for the origami he stole.

In Amazon's World Diend appears again looking for the GaGa Armlet. Diend manages to infiltrate the Dai-Shocker base and learns the armlet is in the possession of Llumu Qhimil. He joins Decade and Amazon in a fight against the ten faced demon and after GiGi Armlet is stolen from Amazon, Narutaki presents Kaito with a card that will make Diend stronger on the condition that he defeats Decade. Kaito takes the card but says that there are other options as well. Kaito then appears to tell the Hikari Gang that the boy who stole the GiGi Armlet, Masahiko is being subjected to Dai-Shocker's Human to Monster project. Diend then battles with Decade and Amazon having recovered the GiGi Armlet and manages to steal the GaGa Armlet from Llumu Qhimil until Decade uses an Attack Ride Card to take it from him. The riders then destroy Llumu Qhimil and Diend joins the Hikairi Photo Studio as a traveling partner into another world. They end up in the worst possible world as they enter the World of the Rider War from Natsumi's nightmare.

In the World of the Rider War Diend helps Asumu kill off Saga and his Fangire Minions. Asumu explains to Daiki that there are some treasures that should never be taken. When Tsukasa goes to save Natsumi, Kaito appears to tell him about the trap Super Apollo Geist has planned but Tsukasa goes anyway, promising Kaito that if he dies Kaito can have the world. Diend helps Tsukasa fight Super Apollo Geist and the revived Kaijin even giving him a Diend Final Attack Ride to destroy Geist. But when the Rider War commences he shoots Decade at point blank range marking future battles.

Movie Wars 2010
In Kamen Rider x Kamen Rider W & Decade: Movie War 2010, Decade Final Chapter, he tries to convince Natsumi to destroy the photographs of Tsukasa as they are only memories of who he used to be as Tsukasa has now accepted his fate as the destroyer of worlds as Decade Violent Emotion.

After Decade is destroyed he and Natsumi meet Wataru Kurenai who explains Decade's role as a substitute for the riders of the A.R. Worlds. When Tsukasa is revived, Diend joins the fight against Super Shocker. After the struggle he is seen with the Hikari Studio gang posing for a picture.

Kamen Rider × Kamen Rider × Kamen Rider The Movie: Cho Den-O Trilogy
Diend reappears in Kamen Rider × Kamen Rider × Kamen Rider The Movie: Cho Den-O Trilogy. In the film Daiki allows himself to become possessed by a Relict Imagin in order to travel back in time to November 22, 2008, and steal a gold-plated gun from the Kurosaki family estate, a heist he failed to perform on that date in the past.

He allows the Spider Imagin to be destroyed and hitches a ride back in time on the DenLiner to attempt to cause a time paradox so he can be arrested by Kamen Rider G Den-O. This sets in motion a series of events that would allow Daiki to complete his plan, by getting his past self accidentally hit by Kurosaki and retrieve the golden gun before it gets damaged, thus putting it into his possession while opening his pursuer's eyes to what he should value more. Although his past self steals the golden gun from him and escapes, Daiki obtains a K-Touch from Kurosaki and gains his own Complete Form and destroys Kamen Rider G Den-O.

OOO, Den-O, All Riders: Let's Go Kamen Riders
Kamen Rider Diend was part of a group of reinforcement riders led by Akira Date/Kamen Rider Birth to aid the primary riders in defeating the Rock Great Leader. All the Kamen Riders got on their bikes and performed the All Rider Break attack which destroyed the Great Leader.

Kamen Rider x Super Sentai: Super Hero Taisen
Daiki and Tsukasa both appeared in a movie alongside the Gokaigers in a Super Sentai meets Kamen Rider, Kamen Rider × Super Sentai: Super Hero Taisen movie. However, Daiki revealed was true antagonist because the timeline was restored and now he against them and two machines merges into one Big Machine.

Rider Powers
He mostly appeared as Kamen Rider Diend. Only in Episode 12 of Kamen Rider Decade, he briefly wore G3-X suit.

Trivia

 * In some materials in Decade, Daiki's surname is spelled in English as "Kaitoh" rather than "Kaito".
 * Unlike Kamen Rider Decade, Daiki can't change into any of the past Riders in the same way he could. The only time he became another Rider was when he briefly wears the G3-X armor.
 * Exactly how and when Kaito stole the Diendriver from Dai-Shocker was never clearly stated, but many fans believe that when he ran away from his world, he stole the Driver while traveling and stealing treasure.
 * He is similar to Basco Ta Jolokia from Kaizoku Sentai Gokaiger, as they both can summon Riders/Sentai.