Yamate

Yamate (山手) is a minor antagonist in the Toaru Majutsu no Index series. An operative of BLOCK he was killed by Etzali who then used his appearance to infiltrate the organization.

Battle Royale Arc
In order to escape an assault by mercenaries of BLOCK unharmed, Etzali decides to attack one of them and take their appearance using his magic; Yamate was the unfortunate victim. What Etzali doesn't know is that Yamate is one of BLOCK's main members, and as such, he couldn't simply slide away unnoticed and is forced to keep himself undercover, indirectly monitoring BLOCK's current activities.

BLOCK never realizes that Yamate had been replaced even after Etzali compromises their plan and escapes the group, though GROUP noticed Etzali's strategy immediately once Tsuchimikado Motoharu saw the real Yamate's mutilated corpse.

Trivia

 * Etzali thought to himself that it was strange that Yamate was someone important for his organization, noting that he was rather weak.