well, so that somewhat confirms his ability, which is honestly terrifying, to take over the body of their killer... but im guessing the specific activation method is having a living being near to witness it (dosnt matter if human or animal) otherwise he wouldnt have asked for a rooster to be present or plan it so dazai would watch him get ''killed'' in the chopper
https://mangasee123.com/read-online/Boruto-chapter-3.5.html