|Full Name||Isori Kei|
|Family||Chiyoda Kanon (Fiancée)|
|School||First High School|
|Voiced By||Sōma Saitō (Anime)|
|Novel||Volume 3, Chapter 3|
|Anime||Episode 8, Nine Schools Competition I|
Kanon is his fiancée.During the disturbance of Yokohama, Kei protects Kanon from the enemy attack, ending up being mortally wounded.
Kei has a good relationship with Tatsuya. Kei is impressed by Tatsuya's CAD calibration abilities. He is also grateful to Tatsuya for saving him using his "Regrowth" magic.
At first, he thought that the magic of regeneration should not be a secret. But knowing the price Tatsuya pay to use his magic, he felt awful to know that Tatsuya had to suffer 150 times their pain, so he decided to keep that skill a secret.
The Isori and Chiba families have close working ties, thus Kei and Erika have known each other since they were young. Kei is responsible for the engravement magic found in Erika personal CAD.