With the source of the announcements getting louder, the benefit of having two other people here, and time potentially running out for Martin, Kokichi makes a split-second decision to take a risk. Worst case scenario, he dies, and he was supposed to be dead already anyway, right?

He adopts a panicked expression for the benefit of his companions on the ground and, as the sound of the drone gets close, shifts slowly as if he's trying to stealthily better hide himself. He intentionally leans too far so as to "accidentally" tumble out of his tree with a totally surprised yelp, catching a branch on his way down to slow the landing so he doesn't actually hurt himself.