The Sumi is a rare and precious flower known only to the members of the Hisomu Clan. The flower's black petals can be distilled into ink, and its powerful toxins used to create ability-enhancing tattoos known as the Mark.
Sumi grows in the desolated city of Tabriz where bandits currently infested in. A merchant told Tetsuji about the Sumi and he used it to become young. However, he become maddened by the killings and died under the flying ravens. After this incident, the Hisomu Clan use the Sumi to protect themselves. The Sumi are usually used by the younger members of the clans so that the master can control the madness. 50 years prior to the events of the game, the Hisomu Clan and the bandits made an agreement for the ninja protect the bandits' 'exports' and the bandits protect the flowers. Eventually the bandits realised the potential of the flowers and turned their back. The clan sent Dosan to deal with the situation. Soon, the Sumi had been dead and Azai was the only one who knows. Most of the Sumi the clan have aren't fresh which Dosan noticed when he paint the ink into his body. This make the Marked Ninja the last one. The remaining Sumi is painted into his body gaining him Serenity.