So they think they would be able to kill a Broly-tier character with a damn WWII ship? The same guy that turned your whole capital city into a parking lot with just a wave from his hand? At that point even talk-no-jutsu sounds better for god sake.
Every chapter Fukuda looks a bit more insane than before, at this pace it's a matter of time for her to snap and go crazy over Nakano or any female that approach him.
So they're like some sort of entity that is programed to die at a certain event caused by specific prior actions/interactions, so if you try to kill it before that it will just keep respawning as a protection for that event fulfillment to succeed, but if it goes sentinent and don't follow that...
The only way i can think the MC keeping the USB is that the author hide that he was actually a complete psycho that want to get off to it and actually enjoyed all the suffering he gave to his family, friends and now throwing the girl under the bus, but probably it is that he's just an idiot.