KittyKiero
The Iwatobi Scarlet
The doctor has lost someone dear to him, thanks to a dirty organization, and now he seeks vengeance. For years now, he's been researching the possibility of longevity or immortality. He's gone through many lab experiments on (mostly) involuntary test subjects, including himself.
So far, he was the only one that didn't die.
That was until he found her.
Trying once more, a young girl managed to build an immunity to his attempts on eternal life. It is not yet known if she will live forever, but she has gained abilities and lost memory of the outside world. All she knows of is the mysterious doctor she's being tested on and used by.
The doctor and the subject work together to attack and bring down the fiendish organization, all while studying the possibility of eternal life.
(MxF; Roleplay with detail; Two paragraphs minimum; blah, blah, bacon... Other stuff. The basics.)