Triage X editor Kawanakajima also stated that realistically, no one in the world could inherit Daisuke Satou's vision and continue the series the way the original author wanted. They need someone who knew his plans for the rest of the series and the ability to execute it properly. The editor also stated that it is common practice for overseas comics and novels to have multiple collaborators who will continue the series after the original author passed away, but in the case of Highschool of the Dead, Satou is the only one who can write it easily and wants the overseas fans to understand it.
[Source: Anime News Network]