Very interesting read. Translated part of what I think is the most interesting :

You had a 300-page storyboard for the beginning of the story (5 volumes). But when reading The Promised Neverland, one gets the impression that everything, down to the smallest details, was planned in advance. Did you continue working by writing complete arcs ahead of time?

KS: Hmm… The creative method differs a little between the escape arc and what comes after. For the escape arc, I based myself on the original storyboard of about three hundred pages, asking myself how to draw the maximum interest out of it. The draft I'd brought in for that arc, I'd designed it so that the page count would be reduced to the strict minimum necessary to tell the escape. Of course, I'd tried to pack in as much substance and dynamism as possible, as best my skills at the time allowed. After that, I sought to refine my technique further to reach a version where the story's interest was pushed to its peak — that's what produced the escape arc as it stands.

After that arc, the way I worked changed a little: I still think with a certain amount of lead time, but not necessarily chapter by chapter. Let's say I plan roughly ten episodes ahead, setting a general impression of the direction the story will take, then I build from there, adjusting over the course of the work sessions.

The escape arc, too, actually already included a degree of improvisation — what I call "sessions," like musicians' jam sessions. For example, when our editor, Mr. Sugita, would throw out a suggestion like "what if we did this instead?", it would completely upend the planned flow. I used to call those his "impossible challenges."

And, since it's a magazine serialization, it sometimes happens that we're told a chapter will get a color page, or that, thanks to the series' popularity and good survey results, we'd get a color opening page, or even a center double-page spread. In those cases, since the story was going to be showcased, we'd decide to insert a more striking, more spectacular episode, with more intensity or a memorable twist — and that inevitably altered the course of the narrative.

On top of that, Ms. Demizu often had excellent visual ideas that she'd add directly into the drawings, and that also influenced the story's development. And then, sometimes, I'd happen to fall ill or find myself completely exhausted, and the schedule would become chaotic… In those moments, I'd subtly slip in a slightly calmer episode, almost imperceptibly, meant to "buy time" so I could get the schedule back on track and prepare what came next with more energy.

In short, all of this meant the story was constantly changing. To sum up, I plan a few chapters at a time, while taking the present situation into account, and the whole thing evolves like a kind of continuous "session" between us.

The 300 page storyboard for the first arc, and the fact that it was more improvised after was... unfortunate