Neither. It's the manipulation of spiritual and physical chakra to create unique techniques that can be utilized in battle. It can be utilized in taijutsu, which is a striking art I will teach alongside ninjutsu, and also involves weapons techniques, cloning and shape transformations, movement control, elemental transformations, and more. In my world, it's only taught to ninja, but given the similarity in some of the techniques to the abilities I've seen from various blood types, particularly Coldblood and Darkblood, I believe it could be helpful to many here.