After Du You entered, those Doppelgangers had already left in advance. So many Doppelgangers together could come up with any excuse, and there would be absolutely no flaws, no one would doubt their motives.
Du You entered an army camp and then started the action. With so many people, relying on Du You to kill them all by himself would take who knows how long, even if they wouldn't move. But Du You is, after all, a summoner.
After spending some time, Du You summoned a large pack of wolves. Though they were just ordinary wolves, killing a soldier without resistance was no problem. The wolves entered the camp, found each soldier, then bit their throats or clawed them open, and moved on to the next.
The soldiers with throats cut open could only wait for death. Unlike a heart, there's no worry about it being on the right side or anything.
