Sadako Yamamura
In "Loop", protagonist discovers that he is actually a clone of Ryuji, who realized he was living in an artificial world right before his death and asked the outside world to help him escape. Kaoru realizes that he is the cure to the virus that afflicts his girlfriend, Reiko, and is implanted into the Loop; in order to obtain the cure to the virus to save his girlfriend, he has to die. When in the Loop, Kaoru is reborn through Sadako instead of Ryuji, and Kaoru from then on lives under the name of Ryuji Takayama. After six months of research, Kaoru/Ryuji creates a vaccine for the Ring virus, a sample of which he gives to Ando. The vaccine is then mass-produced, neutralizing the effects of the Ring virus. He also creates a virus designed to accelerate the Sadako clones' aging rate and kill them, ridding the Loop of Sadako Yamamura forever. However, the virus also affects Ryuji, and he eventually dies his second death. His last thoughts are of Reiko and her face.