Cell's sister, Uracil, suffers from an unknown disease since she was born. Cell became a successful medical doctor but he still can't find a cure for her. Together with another doctor, who happens to be his ex-girlfriend Fenyl, that works in the same clinic with him, they devise an unconventional method that might save Uracil, where everything else already failed. The plan is to make changes in her DNA so it can fight the pathogens eating her from inside. To do that, they have to try cultivating different strains in Cell's body and inject them into her body in a way that won't be rejected by her immune system. And the only way to do that is by sex...