Yasuko and Kenji(2005)

Yasuko to Kenji

About a man named Kenji and his younger sister Yasuko, whose parents died in an accident 10 years earlier. Kenji was once the leader of a gang, but in order to support him and his sister, he began making a living as a shojo mangaka. His character normally wears glasses and appears to be a gentle guy, but he throws off his glasses and reverts to his violent side whenever he tries to protect Yasuko from danger.

(Source: Tokyograph)