We don't know the answer yet, but we can still speculate.
Summary:
- Copies of the storyboards for the Look Back manga will be given to some moviegoers in Japan.
- Some fans misinterpreted the announcement as Fujimoto doing storyboards for the adaptation, but that's not the case.
- We don't know how much he's involved, but he was possibly overseeing the production.
An official announcement posted by the X (formerly Twitter) account of the Look Back movie somewhat confused Western fans. The post simply states that people who go to see the movie in Japanese theaters will have a chance to win a copy of the original storyboard for the manga.
However, the automatic translation suggests that the storyboard is for the movie. Combined with the fact that it mentions Tatsuki Fujimoto as the original author, some fans have already jumped to the conclusion that Fujimoto drew storyboards for the movie too — but nothing actually suggests that.
Most of the Time, Mangakas Don't Draw Storyboards for Anime
In fact, it's pretty rare for the original creator of the manga to actually be involved with the adaptation — storyboard or anything else. At best, they're involved with the planning stages, but they usually don't do any animation work. It's easy to understand why, as animating something requires a completely different skillset.
The most notorious cases of this actually happening are people who are both mangakas and established anime directors already. Hayao Miyazaki adapted his own manga series in Nausicaä of the Valley of the Wind (Kaze no Tani no Nausicaä). Junichi Satou was responsible for both the anime and the manga of several of his works, such as Magic User's Club (Mahoutsukai Tai!) and Princess Tutu.
It actually was reported before that Tatsuki Fujimoto was already heavily involved in the production of the adaptation of his most famous hit, Chainsaw Man. However, that information was simply another mistranslation.
Fujimoto did not draw the storyboards or write the script for the Chainsaw Man anime — as he was only mentioned in the credits as the original creator. That said, Fujimoto still oversaw the production process, meaning he had at least some creative control.
We Don't Know How Much Fujimoto Was Involved in Look Back Anime
While there's nothing that suggests that Fujimoto was involved in the creation of anime more than usual, it's still entirely possible that, just like in the case of Chainsaw Man, he had some indirect creative control over it.
Still, there's nothing in the original post that gives any information about Fujimoto's involvement. That said, since copies of the manga's storyboard are being given out, fans guess that Fujimoto was at least involved with this decision.
Ultimately, we won't know the truth until the movie releases with the full list of credits.