
According to the mangaka, Kazuna Uchida, the character who grows the most during the story. She even considers that she wrote the manga to follow the growth of this one young man. The novel version of I Shall Never Return is actually written from Ken's point-of-view. 
The mangaka most enjoyed writing the character as the bad boy he was when the series started. Eventually he started to change and grew more positive.

Amafuji Ken longs to tell his best friend Youshinari Ritsurou how he really feels. In the way of that admission is Ritsurou's girlfriend, Moeko. After dropping out of high school, Ken gets Ritsurou to live with him.The angst begins when Ken sleeps with Moeko to get to Ritsurou. 

Upbeat Ritsuro and downbeat Ken have been longtime friends. Although Ken leads a dark life of prostitution after dropping out of high school, Ritsuro still cares about him. When Ritsuro realizes that what Ken wants is something more than friendship he vacillates between Ken and his girlfriend Moeko, setting the stage for a bizarre love triangle.

Got some time?

Ken Amafuji