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.
It grows on the desolated city of Tabriz where bandits currently infested in. the merchant told Tetsuji about the Sumi and he use to become young. However, he become maddend with the killings and died under the flying ravens. After this incident, the Hisomu Clan use the Sumi to protect their survivability. The Sumi are usually used by the students so that the master can control the madness. Azai comment whether they make you mad or dangerous and that they are no difference. 50 years ago before the game, the ninja 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. Dosan is able to scare, knockout and a little bit killing the bandits that the chief forced to give up the Sumi. 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.