What Kazuichi feared the most was an inevitable event in the apocalypse. And no matter how diligent he worked to suppress that inevitable, ultimately there was nothing he could do about it.
The appearance of the Aberrants was one thing, and Kazuichi realized that these Aberrants were bound to evolve further.
Thus he went on missions, destroying every Aberrant's nest he could find while he made his way back home.
Nevertheless, that gesture wasn't enough. Despite his hard work and zealousness to rid the world of the infected, there was only so much he could do.
Besides, later on, Kazuichi learned that the entire world was suffering from the apocalypse. When Japan was infected, it had already been a couple of weeks since the zombie apocalypse had commenced.
The only reason why the masses didn't know anything about it was because the governments tried to keep it under wraps.
