Dokaben is a baseball manga by Shinji Mizushima, serialized in Weekly Shōnen Champion magazine. It was later made into an anime by the same name. It was immensely popular in Japan during its original release, and in sports manga of all time it likely ranks second only to Slam Dunk by Takehiko Inoue.

A dokaben is a kind of bento box which the protagonist, Taro Yamada, likes to eat.

(Source: Wikipedia)