Not necessarily for viewing. 1. It is unlikely that you will find "Another Gantz" in Russian (I hardly found with Spanish subtitles).
2. "The Other Gantz" was released the day before the premiere of the second part of the film ("Gantz: The Perfect Answer") and is essentially a bridge between the two films in the style of "in the previous series".
3. On 90% (maybe more) consists of the video sequence of the first part of the film "The Gantz".
4. Those 10% that remain are minor little episodes with characters from the first movie, not really expanding the understanding of the characters.
5. Accept that this is not a full-fledged film, but just a crumpled retelling of the events of the first part of the film, wrapped in this format.
Result: You should not waste time and effort searching for this conditional film and especially watching it. You will not lose anything, at least because at the beginning of the second film there is a short retelling of the events of the first.
There is nothing negative in the video itself. Therefore, the review and neutral.