In the Neo World, they still sometimes act like their RoD forms. For example, when Nagito acts like an insane person, it isn't because of his sickness, no, it's because his RoD form in showing its personality. Same thing applies when TeruTeru decided to kill Imposter. It's just his RoD showing himself.
Same thing applies when it come to the Despair Disease. RoD Nagito lied a lot, RoD Akane cried constantly, RoD Ibuki was gullible and easy to manipulate, and RoD Mikan... We all know how RoD Mikan is.
