Koujiro Rinko

Professor Koujiro Rinko is a scientist, former love interest, and co-worker of Kayaba Akihiko. She attended Touto University in Japan and was a part of Shigemura Lab in the Electrical and Electronic Engineering Department.

Background
Koujiro Rinko met Kayaba Akihiko in her first year of college at the age of 18, when she invited her senpai to go swimming. Kayaba was 19 years of age at the time and a second year.

Soon afterwards, Koujiro Rinko began working on the SAO project, unaware of Kayaba's mastermind plan. Ten years later, the first VRMMORPG Sword Art Online was released.

Sword Art Online
She initially helped in the development of SAO and, when the SAO incident occured, she was the only person who guessed where Kayaba was. Without telling anyone and avoiding the police, she decided to confront Kayaba in his hidden mountain cottage with the intent to kill him, but she was not able to do so and instead helped maintain Kayaba's physical condition, when he dived into the game for long periods of time. After the incident, the police found the cottage where both of them stayed. While Kayaba had already died after digitizing his brain to the network, Rinko was arrested by the police and awaited her trial.

ALfheim Online
After the ALO incident, Kazuto wanted to find out more about Kayaba and his World Seed. He got hold of Rinko's email address and asked if they could talk. A week later Rinko replied, and she went to Kazuto's house, where they decided to go to a coffee shop near a Tokyo station to talk. Apparently, she was released on bail from her trial and later acquitted. Though it is later revealed that before the SAO incident ended, Kayaba had implanted a fake long-distance micro bomb to the left of her sternum to make the world think that she was forced to help Kayaba during the incident. According to Rinko, that was the only gift that Kayaba had given her. .

Project Alicization
It has been 2 years since the SAO incident. Rinko has apparently moved to San Francisco, America. She has been invited by Kikuoka Seijirou to do a top secret research on FullDive technology, but has been reluctant to accept the offer, until, one day, she received a long mail from an unexpected person, who turned out to be Asuna. After learning about Asuna's situation, she agreed to help the girl find Kazuto, so she contacted Seijirou about accepting the invitation. Rinko and Asuna, then disguised as Rinko's assistant, travelled to the hidden base of RATH, the Ocean Turtle. There they witnessed RATH's research on the «Soul Translator» and learned the reason why Kazuto was secretly transported to this facility.