Sword Art Online has an expansive list of characters, but few play a critical, recurring role throughout the entire story. However, one character who does is Seijirou Kikuoka of the Japanese Self-Defense Force. He is the driving force for Kirito to become an investigator in the VR Network, eventually leading him to join the Alicization Project.
Originally, Kikuoka was one of the Beta testers for Sword Art Online, but rather than transferring over to the full release of the game, he used the information he gathered to begin developing Project Alicization, so he wasn't trapped in the game with the other players. He then joined ALfheim Online to gather information after the SAO Incident and he lured Kirito into the counselor's office at the SAO Survival School in the real world to discuss the events that took place. Kirito explained everything that he encountered starting from when he learned that they were trapped in the game. It was at this time that the two discussed Kirito joining ALfheim Online to rescue Asuna after Seijirou, under the Chrysheight username, gave him the name of the hospital Asuna was at in exchange for information about the SAO Incident.
A year after the SAO Incident, Kirito was approached by Seijirou to investigate rumors about the Gun Gale Online game and its connection to real-world deaths. It's decided that Kirito will convert his ALfheim character to the Gun Gale game in order to draw the attention of the killer, <<Death Gun>>, during the Bullet of Bullets Tournament. After learning about Kirito joining the game, Asuna approached Seijirou to seek permission to log into ALfheim Online for a meeting with him, where she confronted him about Kirito's conversion to Gun Gale. He eventually caved and explained the situation to her.
After the Gun Gale Incident was taken care of, Seijirou's status as a Lieutenant Colonel for the JSDF was revealed when he offered Kirito a job at Rath. The job was to test out the Soul Translator, though this was just a ruse. The true goal was to create a Bottom-Up AI for the military. Later, Seijirou and Higa Takeru kidnapped Kirito's body after being put into a coma so they could reconnect him with the Soul Translator and undo the brain damage caused by the attack.
After the abduction, Asuna was able to infiltrate the Rath base and confront Seijirou about abducting Kirito, during which he explained the reason for the abduction and what his plan ultimate plan for Project Alicization was. After the attack on Ocean Turtle base, Seijirou allowed Asuna to enter Underworld with a high-ranking profile to stimulate Kirito's Fluctlight and help his recovery. After the War of Underworld had concluded, Seijiro once again contacted Kirito after someone infiltrated Underworld.
Seijiro Kikuoka has been a master manipulator since he met Kirito and Asuna. He never reveals the full truth willingly, only divulging bits and pieces. While some confidentiality is expected from a member of the JSDF, he has no problems manipulating civilians -- not to mention minors -- in order to achieve his goals. He manipulated Kirito into entering the Soul Translator under false pretenses and kidnapped him after he fell into a coma. While this was done to accelerate his recovery, it's still illegal and it took Asuna and co. digging deep and putting the pieces together to figure out where they took Kirito. While Seijirou Kikuoka isn't necessarily an antagonist, he isn't innocent either. His actions may have good intentions, but they also have dangerous consequences.
