(REVIEW ORIGINALLY WRITTEN ON 01/22/2021, IDK WHY I WAITED UNTIL NOW TO POST THIS HERE)

Having finished the manga 2 days ago as of writing this, this was a very compromised adaptation.

In an effort to make the movie more appealing, the plot of the Osaka arc is slightly altered to make it more approachable, considering this was like the last arc before the final one.

On that note, a lot of characters were strangely absent, namely Sakurai and Kaze among others. I do understand some of these changes, namely leaving out Takeshi, since his big moment likely would've been lost on any viewers who hadn't read the rest of the series until this point. As such, the main Tokyo team is now down to Katou, who strangely in this movie is portrayed as being new to the game despite being revived for this battle and Kurono leaving in the manga, Reika, and Suzuki, again kind of understandable since a casual viewer would have had no idea who this person was without this. On a similar note here, Kurono dies in the previous fight, shown in a flashback in the very beginning, instead of winning the game and choosing freedom.

However, there's a straight up flashback at the end of the movie that shows a large portion of the main cast and Katou choosing the 3rd option in place of Kurono. So, what the hell? Also the plot changes make some details make no sense in context of where this takes place in the manga. Such as the participants not knowing at this point that failure to defeat the target simply lowers their points to zero instead of them dying. I guess you could say this was done to create at least some tension for, again, anyone who hadn't read the manga until this point and is just watching this movie casually.

Man with all these weird story compromises you'd think the better option would have been to just make a full CG movie series, as expensive as that probably would've been. It honestly would've worked better than continuing with the previous adaptation or making a new one on a TV budget.

And speaking of the CG, the positives; this movie looks fucking amazing. The characters themselves look as if they jumped right from the manga and the animation is really good, likely due to the fact that the manga was made using a lot of 3D software to begin with. Its in the same camp of Adventures of Tintin imo. Whereas that movie went for a more realistic look while also having its characters stylized enough to not look uncanny, Gantz:O is adapted from a source material where its characters kinda just look like that to begin with. Also the action is stellar, and just as much of a blast as the manga's version of the battle. And in my opinion, that's the main thing to nail when adapting a manga like Gantz.

I'd recommend this to an existing fan of the manga, though the odd plot changes will be even more pronounced then. As for someone who isn't, you could do worse.