Ken

A teenager who is an expert in knife throwing. During his stay with Nijū-Mensō, his role during a job was usually more in the execution stage than the planning or preparation stage. He was the one who originally shortened "Chizuko" to "Chiko", a nickname which Chiko quickly picked up on. Chiko calls him Ken-nii-chan (lit. older brother Ken) as he appeared to be the youngest member of the band save Chiko, and the two were very close. He was the one who taught her to throw knives. He lost the vision in his left eye after being attacked by Tiger. After the train incident he went off on his own after waiting several days for Nijū-Mensō to come back for him.

Although he was once cheerful, he appears to harbor bitter feelings toward Nijū-Mensō for abandoning him and Chiko for having companions who alleviated the loss of Nijū-Mensō. Later, however, it is revealed that he still has a soft spot for Chiko and helps her and the passengers on a crashing airship escape, soon after Nijū-Mensō disappeared a second time. (Source: Wikipedia)