When the Spirit has awaken, a spirit mark will appear on the master's body. A Spirit Master can hide this mark. Suppressing the spirit mark is quite easy, like breathing. Even though it is very easy, succeeding on the first try is considered an outstanding talent. If masters imbue their spirit mark with enough spirit power, they can release it outside their bodies. It only lasts for a short time and there's no practical use for it.
Spirit Marks are not in the LN