Saraku

Saraku is an esper and operative of MEMBER.

Battle Royale Arc
He is apparently killed after trying to delay Accelerator who was on a mission for GROUP; however, the Professor later disclosed that MEMBER should recover him since he's still alive.

Ability
His ability is Kill Point (死角移動). He can teleport behind a person, but since he cannot calculate the theoretical value of the 11th dimension, he needs to know that person's current location in order to activate his ability.

His ability wasn't originally called Kill Point, but it's a name that Accelerator calls it since Saraku couldn't teleport through calculations involving the 11th dimension, and the Professor seemed fond of the name.

Power Level
It is unknown if his Level is actually 4; Accelerator noted that an esper who's able to teleport their own body is already considered a Level 4, but with the impairment of not being able to calculate the 11th dimension, a failure like Saraku couldn't be good enough to be a Level 4.