Does Eren have to be in contact with a titan with royal blood or an eldian with royal blood to activate his founding titan commanding powers? Supposedly Eren have to be in contact with someone of royal blood to activate his founding titan habilities to command other titans. Does he have to be in contact with a titan with royal blood, or can just be a human non transformed eldian with royal blood to activate those powers?
According to the latest manga episode it is said that he has to be in contact with a royal blood to activate his power of founding titans and they also proved this when they recalled how the very first time eren was able to control titans, that was when he hit diana(his stepmother,a royal blood) and that time he wasn't in this titan form.
So from this we can say that he just had to be in contact with the royal blood to activate the power of titan