20th Century Boys (vol. 07) by Naoki Urasawa, with the cooperation of Takashi Nagasaki, English adaptation by Akemi Wegmüller
Even as he is pulling his body – mid-escape! – out of the tiny hole that will release him from the infamous Umihotaru Prison, manga artist Kakuta momentarily gets distracted: "Whenever I run into anything that would make good material for a manga, I get totally absorbed"...