Pure Grimoire

The Nameless Grimoire (名もなき魔道書), also known as No Name (ノーネーム), is Mai Natsume's grimoire and was responsible for turning Mai into a girl as its vessel has to be female. Its principal ability is allowing the person with whom it has fused to read the thoughts or memories of the people she tastes. This can be either by kissing or licking them directly, but it can also function by tasting their blood. In addition this ability works on objects, and it allows the vessel of the grimoire to obtain information both about the object itself as well as information about those that had used or created an item.

In addition to that power, the grimoire allows its vessel to regenerate her injuries as well as to greatly boost her strength, speed and endurance. When Mai's physical abilities are enhanced, is able to use unarmed strikes to cut through a chain as well as to shatter stone.

The grimoire itself is sentient and is capable of communicating with its vessel when she is unconscious. It appears to be interested in increasing its power, something it was able to achieve after absorbing for a fragment of the Azure a time.