Proper Japanese Title: 世紀末リーダー伝たけし!
Originally serialized in Weekly Shonen Jump.
This was Mitsutoshi's first major success until he was arrested and convicted for breaking child prostitution laws at which point Jump abruptly cancelled the series. Due to this abruptness, the series was never fully collected in this format and it wasn't until a few years later it was released in a new format (see here) to finish collecting the series (this time under a "seinen" imprint). Mitsutoshi would later became a popular artist in the magazine for a second time with Toriko which launched in 2008 (he had published a pilot of Toriko in WSJ in 2002, suggesting he was always intending to follow up Seikimatsu with it).