Enzu

Enzu (円図) is a background character referred to in Shinyaku Toaru Majutsu no Index. He is apparently a patient in Yakumi Hisako's hospital in School District 13.

Background
Enzu somehow finds himself in Hisako's hospital. The tests conducted on his person is apparently on new assassination techniques, and as with Hisako's reaction to their well-being, unlike Akinai, and it makes him expendable like Kevin.

Agitate Halation Arc
After Tsuchimikado Motoharu is defeated by Kamijou Touma, allowing for Hisako to escape the former's wrath. Hisako states what other jobs she needs to deal with at the moment, to which Rensa, her assistant, responds that the private clinical test of the Designers' Gel that rearranges the structure of cholesterol has begun. The amounts are being carefully adjusted to acquire accurate data, but the thrombus should be complete in about a week. Apparently, the tests done on him is being used to make an assassination weapon that would slip past any forensic investigation.

It is unknown if he is still alive after the defeat of Hisako.