別冊 少年サンデ [Bessatsu Shonen Sunday] [Separate Shonen Sunday]

A companion magazine to Weekly Shonen Sunday, Bessatsu Shonen Sunday ran monthly from 1960 to 1974, offering Shogakukan readers a deeper dive into serialized stories and one-shots. It served as a vital incubator for the publisher's manga talent during the golden age of boys' weekly magazines, providing a space for experimentation beyond the flagship title's pages. While its 113-issue run was relatively short, it captured a transitional era in Japanese comics, bridging the post-war boom with the rising sophistication of the 1970s.