Author's Note: "Donatello's Demise" is a sequel to my fan-fic "The Girl Next Door." You will probably have an easier time understanding the sequel if you read the first one, but if you don't want to take the time to, I have written a synopsis which highlights the main points of "The Girl Next Door."

Disclaimer: Teenage Mutant Ninja Turtles, all related characters, and all derived works are the intellectual property of Nickelodeon, Viacom, Eastman, and Laird. This story is for entertainment purposes and not for monetary gain. In no way should this story be taken to be anything other than a fan-based expansion of and commentary on the original work. n00btmntfan is in no way associated with the makers of TMNT.

In "The Girl Next Door," a Japanese woman named Satou Atsuko moves into the apartment directly downstairs from April. Satou is a computer programmer, collector of traditional Japanese weapons, and an avid disciple of ninjutsu. After an unfortunate encounter with April's mutated father, Atsuko befriends April. April, who is struggling with being torn between Donnie and Casey, confides in Atsuko more and more. However, unbeknownst to April, Satou Atsuko used to go by a different name—Tang Mei. Tang Mei was the older sister of Tang Shen.

Shredder and Splinter, it turns out, had made a childhood pact when they were in school: Splinter, who was enamored with Tang Mei, and Shredder, obsessed with Tang Shen, agreed that they would help each other win the object of their affection. However, Tang Mei ended up marrying a man named Kobayashi Kenshin. Splinter accepted this and moved on—only to discover that Tang Shen had loved him the whole time. When Tang Shen chose Splinter, Shredder saw it as a violation on Splinter's part of their childhood contract. When Shredder finally decided to finish Splinter off, he decided to make Splinter suffer first. So, he captured the Kobayashis and made Tang Mei watch while he killed Kenshin and their sons Kenji and Suki. Then, he planned to capture Splinter and make him watch while he raped the woman who had once been the object of Splinter's affection. However, when Shredder failed to capture Splinter (thinking him dead in the fire), Shredder dealt with his anger by repeatedly raping Tang Mei over the one year he kept her prisoner.

After she had been captive for a year, Tang Mei managed to escape. She changed her name and sought a new life, devoting herself martial arts and learning advanced computer programming. Years later, she gets a job offer in New York and moves there—into the apartment below April's.

Donnie is working on a supercomputer to help him find the retro-mutagen, and April hopes to enlist Satou's help in the matter. However, April's life is complicated by the triangle she feels stuck in with Donatello and Casey. On the one hand, Casey makes her giddy with excitement and she really likes him (plus, there is the bonus of his not being a giant turtle), but on the other, she feels that she owes Donnie for all of the things he has done for her since they met. Eventually, after much agonizing over it, April ends up dating Casey—however, their relationship ends up being rather short-lived.

The day after Casey and April become an "item," Casey is captured by Karai, who has learned of Casey's own sordid past. As a recovering alcoholic, Casey is very vulnerable to relapse. Using that against him, Karai asks him to help her capture April. Unable to resist the alcohol, Casey agrees to help her in exchange for satisfying his addiction.

Eventually, Satou figures out that April is connected to Splinter—whom Satou partly blames for Tang Shen's death as well as her own torment at Shredder's hands. Satou is with April when the Foot Clan, using Casey's tip, track April down. Satou thinks that April is part of a trap set by the Shredder, and wanting to escape she ends up knocking April out—who is then promptly taken away by Karai.

Satou realizes her mistake and manages to find the turtles using April's t-phone. The turtles think that Satou is with the foot—and by the time they figure everything out, it's almost too late. The turtles then rush off to save April, leaving Satou and Splinter alone in the lair. Satou and Splinter reconcile.

Meanwhile, Shredder is planning to rape April as another way to punish Splinter. He almost does, but then the turtles burst in to save the day. Michelangelo is grievously injured and April is severely traumatized; however, it is unsure whether Shredder survived the encounter.

When Satou and Leonardo go to find Casey, they discover the truth. They give Casey two days to either tell April himself or to just break up with her and never speak to her again. Casey is too ashamed of the truth and so he chooses the latter option. Donnie, who learns the truth from Leo, decides that April deserves to know the truth too, since she is so upset by Casey's mysterious dumping of her.

Furthermore, April has started to suffer from PTSD; her father is the only psychologist who will believe the strange situation is true. Donnie doubles his resolve to fix Mr. O'Neil so that Kirby can help April recover. Donnie swears to April that he will never rest until he finds a cure. Then, to his surprise, April declares that she loves Donnie and they kiss.

The story ends with Satou Atsuko reclaiming her identity as Tang Mei. The turtles adopt her as their aunt. She decides that she will finally heal from her old traumas and resolves to help April overcome her PTSD.

Now, on to the sequel...