Saigo

Saigo (災誤) is a character introduced in Toaru Majutsu no Index. He is a teacher in A Certain High and is the bane of the students there.

Etymology
Somewhat befitting his nature among the students, his name can be translated as "Disastrous Mistake".

Appearance
A large man, he is described as gorilla-like and musclebound, so large that a four door family car looks crowded for him. His walk is described as lumbering.

Background
He is the teacher in-charge of student counseling in A Certain High, and there, apparently earned a bad reputation with its students. Oyafune Suama has a whistle that allows her to call him when she wants students to be "counseled". The man apparently knows martial arts and can get very physical against his trouble-making students. According to Kamijou Touma, there is apparently a legend about him in which he managed to catch a falling boulder with both hands while in a rockfall zone, though it is unknown if there is any truth in this statement.

Document of Constantine Arc
He makes a brief appearance at the beginning of the arc where he is called by Oyafune Suama to prevent the re-ignition of the fight between Touma, Tsuchimikado Motoharu, Aogami Pierce and Fukiyose Seiri.

Acqua of the Back Arc
He reappears with his car after eating in a restaurant while Touma's class tries to make a break from the campus to get lunch from a nearby convenience store. Due to the fact that they haven't eaten yet while they saw him coming from a restaurant, enrages the students. However, they are forced to flee as Saigo gives chase. Motoharu sacrifices Aogami Pierce, but is promptly ignored by him and chases Touma's group instead, and later Touma alone when the others split off from him. Meanwhile, Itsuwa, who was assigned by the Anglican Church to protect Touma from Acqua of the Back, mistakes Saigo for the God's Right Seat member, having never seen Acqua of the Back before, and tries to attack him. The chase is brought to an end, and Saigo is apparently forced into a retreat due to "health" reasons, much to Touma's relief, allowing him to get lunch.