Another Gantz (video release 2011-5-13) is meant to be watched between Gantz (殺戮都市) Part I and Part II (Perfect Answer). It rehashes significant footage from Part I, and adds only a few unimportant details about a few supporting characters. It was shown on Japanese TV right before Part II was shown in cinema. I think it is only a poor excuse to attract people to watch Part II without showing Part I on TV for free.