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Tear Jerker: Kamen Rider Ryuki
"In this war, there is no justice. All there is, is a pure wish."
As 2002's entry into the Kamen Rider franchise, Kamen Rider Ryuki is arguably one of the darkest seasons in the series' nearly 40 years history, especially since it came at a point where every season up until then had been completely unambiguous over good-and-evil. Based around a war between the 13 Kamen Riders, Ryuki has the highest body count of major characters out of any Kamen Rider season, one of the casualties being the main character himself. Needless to say, expect tears to be wept as character after character are consequtively killed off.
Warning: this page contains unmarked spoilers.
Shinji's Heroic BSOD when he is tricked into believing that Goro was Zolda and he has killed him. It culminates in a cacophony of his own voice in his head, first all talking over one another but converging to all say, "I took... I took that man's... life."
For those that don't count as Pay Evil unto Evil or horror (like Scissors getting eaten by his own Contract Monster), most of the Riders' demise qualify as this.
Shinji Kido/Kamen Rider Ryuki: After deciding to fight in the Rider War to save Yui's life, Shinji spends most of the last five episodes going against everything he had believed up until then. But after Yui dies, Shinji comes to terms with the fact that taking another life to save Yui wouldn't make her happy. Realizing that his wish as a Kamen Rider is to stop the Rider War, Shinji goes to battle against an army of Raydragoons that have began an all-out assault against the real world. However, while saving a young girl in his un-transformed state, Shinji is stabbed by a Monster and fatally injured. Mustering enough strength for one final battle, Shinji dies in the real world, encouraging Ren to live even as Ren pleads for Shinji not to die.
Shinji: I just realized that I do want to close the Mirror World. I'm sure it will cause alot of pain, but I still want it to end. I don't know if it's right or wrong but as a Rider, I have a wish I want fulfilled, and this is it.
Ren Akiyama/Kamen Rider Knight: Deciding to fight as the final Kamen Rider to fulfill his wish, Ren faces off against Kamen Rider Odin in a hopeless battle. After using his Final Vent against Ren, Odin suddenly convulses and is destroyed by Shiro leaving Ren as the final Rider. Using the prize in the end to revive his girlfriend, Eri, Ren spends what remaining time he has alive to make his way to the hospital so that he may die by her side (all to the background of a monologue by Daisuke poetically describing the exact nature of the Rider War).
Shuichi Kitaoka/ Goro Yura/Kamen Rider Zolda: After deciding to quit the Rider War, Kitaoka decides to go to battle one last time against Asakura, deciding to take some responsibility in the latter's transformation into a Rider. By then however, his cancer has progressed to such a point that he dies from it before he can fight Asakura, prompting Goro to take up the fight in his master's place. Not as experienced as Kitaoka, however, Goro is killed by Asakura.
Takeshi Asakura/Kamen Rider Ouja: After killing Zolda, actually Goro in Kitaoka's place who had by then already passed away, Asakura becomes overcome in grief, partly in knowing that his arch-nemesis had not met his death in the way he had wanted, and partly out of confusion over why Goro would choose to sacrifice himself in Kitaoka's place. Unable to control himself, Asakura rushes out into a police ambush where he is gunned down like a dog.
Miyuki Tezuka/Kamen Rider Raia: Looking into the future, Tezuka predicted that the next Rider to die as a result of the war would be Shinji, but rather than telling this fact to him, lied that he would be the next Rider to die. In a battle against Asakura, the man who ruined his best friend's life, Tezuka is aided by Shinji although even then, Asakura is too vicious for the both of them to handle. When Asakura is about to deal a finishing blow to Shinji, Tezuka makes the decision to put Shinji's out of harm's way only to receive the blow for himself. Dragging Tezuka back to the real world, Shinji begs for Tezuka not to die as it would only mean he was accepting fate. Then, Tezuka explained that he'd lied about his earlier prediction and in his last moments, lets himself be overcome with the joy that he had saved Shinji from the fate he could not save his best friend from.
Tezuka: At last... I changed fate.
Satoru Toujou/Kamen Rider Tiger: Having long been consumed by insanity, Toujou escapes from a three-way battle between him, Kitaoka, and Asakura, under the mistaken impression that he'd killed the other two in a plan of his own making. As he escapes, he invokes the memory of Kagawa (another one of his victims), and wonders if he is one step closer to achieving his dream of becoming a hero. While crossing the road, Toujou sees a father and a son, reminding him of the mentor he'd lost. Suddenly, a truck veers towards them and in perhaps his only moment of selflessness, Toujou shoves them out of the way. As he lays dying, Toujou becomes resigned to his death, wondering what he should have done to become a hero. The next day, the newspapers tell the story of 'A hero that saved a father and son.'
Mitsuru Sano/Kamen Rider Imperer: The Ur-Example of Ryuki Tear Jerkers (and arugably all Kamen Rider Tearjerkers). Having finally attained his wish of living the good life, Sano is told by Shiro that he cannot drop out of the Rider War unless he wants to become prey to the herds of Mirror Monsters under his control. Deciding to do what he can to ensure his continued survival, Sano attacks Shinji until Toujou arrives, not to help Sano, but to kill him. Dealing a lethal blow to Sano, the man barely escapes unable to comprehend the betrayal of a man he had thought to be his friend. Unfortunately, before he can escape to the real world, Asakura arrives and finishes off what Toujou started. Trapped in the Mirror World without his armor, Sano wanders around trying to find Yuri, a woman he'd become smittened with. Seeing Yuri in the reflection of a mirror, he attempts to call out to her to save him to no avail. As his body dissolves in the corrosive environment of the Mirror World, Sano laments his fate and screams as the Rider War claims its next victim.
Mitsuru: Why did this happen? I... I... I just wanted to be happy.
Not to mention that to fix everything in the end, Yui finally convinces Shiro to let her death as a child stand, so that the Rider War never happens. That final scene, with the grandma Sanako all alone in the store, is maybe the saddest scene in the series.
Fact: When I saw Yui and Shiro playing with their younger selves I bawled my eyes out, it was that moving to me.