Since she is an Elemental Spirit Species that can share her magical energy with the natural world and its Mana, it is feasible for Consort Yu to draw an inexhaustible supply of magical energy from the physical world rather than storing magical energy within her own body. But since she is restricted to a form that is “
humanoid”, even if her supply of magical energy is infinite, there is a limit to her output, so the quantity of magical energy she can practically use is being stopped within the domain of a humanoid Heroic Spirit.