Actually Ren does have red eyes and pointy ears as well, but if one wasn't paying close attention, it could be missed. Also new bat wings.

When Akira got away, Ren took out his knife. It's one of his back-up ones as he saves his best one for fighting in Mementos. He manages to dodge the ball of fire, but tenses up at the gun being pointed at the shadow.

He bares out his fangs and makes a loud hiss. Trying to keep himself from floating despite how angry he is. "If you kill that shadow, I will make you hurt and make sure you don't hurt any other shadows here."