Miyabi Nagumo is a student of Class 3-A at Advanced Nurturing High School and the former Student Council President succeeding Manabu Horikita. Nagumo is a tall, fair-skinned teenager with light blond hair and light blue eyes. Kei Karuizawa says that he doesn’t lack in the looks department but to her he is not someone who can rival the likes of Kiyotaka Ayanokōji. Nagumo is a leader who likes to rule through an iron-fist, and is kind of a man who would expel anyone who tries to oppose him. Manabu Horikita suspects him for expelling 7 out of 12 students from the second year that had Nagumo involved in one way or another. He considers Manabu as his rival and keeps on challenging him, also trying to prove that he is better than Manabu. Despite Manabu already graduating, he now targets his little sister and takes joy in the fact that she is somewhat now directly under his control after she joined the student council. It is later revealed by Ikuto Kiriyama that Nagumo promised the second year students reforms where ones who surpasses the boundaries between classes and are capable of making allies from different classes will be pulled up to A-Class. He believes in the ideology of winning the war at the expense of a battle as he lost to Manabu but was also able to drive Akane Tachibana to the point of expulsion. He is shown to be quite persuasive as he got Honami Ichinose to give up her secret to him without much interaction between them beforehand. Although, this is also due to her gullible and credulous nature. He is also extremely narcissistic, but not to the point of Rokusuke Kōenji. He also likes to make those around him into his "toys", showing his deprave mindset. He is also not afraid to hurt his "toys" or sacrifice them for himself and his benefits such as when he gave Ichinose's secret to Arisu Sakayanagi. He can be livid when things doesn’t go his way such as when Kiyotaka Ayanokōji intervened during his plan to force Honami to become his girlfriend, only to have her saved by Kiyotaka instead. He is also seen to be attracted to hot girls such as Honami Ichinose and Suzune Horikita and tries to charm them whenever he has the chance. He purposely refers to them by their first name after brief interactions and will take whatever chances to get close to them. For instance, he attempted to force Honami to rely only on him by entering a relationship with him as well as prolonging a hand shake with Suzune and looking at her tantalisingly. He has a reputation and aura of being a womaniser amongst the student body but despite that, some still views him in a good light. Nagumo also has a tendency to be overconfident at times as shown in the Uninhabited Island Exam where he approached Kiyotaka Ayanokōji without any of his backup Free Groups in I2. Despite this, he is also shown to be calm and calculative as shown in the Mixed Training Camp where he conducted his plan without displaying arrogance nor confidence unlike his latter confrontation with Kiyotaka.