"Even the strongest want to confess!"

As the title suggest, in order to "supplement" the series, they will delve into the story that could not be fully depicted in the TV series. This includes behind-the-scenes stories related to the show's production, and even the settings of the work and the characters. In each episode, tips about the story and setting of the series are "confessed" one after another from all sides. What kind of confessions will come out?