[1]Isamu Yamanaka (勇山中, "Courage, In the middle of the Mountain") is the name of an S-rank Missing-nin, hailing from the Yamanaka Clan of Konoha ; Isamu is noted to be one of the greatest prodigies hailing from Konohagakure, in particular due to his natural powers which he has had since birth. He's also noted to be incredibly skilled within the various Jutus normally performed by Medical-nin: The infamous Chakra Scalpel in particular.
Also, Isamu is noted for his ability to make use of the Yin half of his Chakra to make use of several unique techniques, of which useage he has become infamous, earning him the epithet of "Isamu of Yin" (勇殷の, "Isamu in No"): The most famous of these techniques being known as Izanami; after his defection from Konoha - Isamu became a full member of the Akatsuki at age 18; giving him ten full years to prove his worth. To this day, he's still trusted by the organization with various tasks; including recruiting new members to their cause.
Isamu is infamous across the Shinobi World as an individual who has never lost a single battle; this is also appearantly due to his ability to look in the hearts of other Shinobi; determine what they fight for and seize control over their very ambitions - using their own emotions - primarily their doubts and fears to force them in knee. He's also feared for the very same ability, as he's gotten families, friends and trusted teammates to turn at one another in the blink of an eye and kill each other before his very eyes; it is also evident that Isamu finds the thrill of turning brother against brother, parents against child and friend against enemy to be highly amusing - believing it strengthens and ascertains his superiourity.
Isamu is known to hunt down any surviving Uchiha Clan members in his spare time for their Sharingan; finding them to be beautiful to behold and maintaining a haughty disdain of the Clan in question; Isamu is especially interested in any remaining Mangekyō Sharingan's and would go trough great lengths to get them, because of how no Mangekyō Sharingan pair is ever alike, he treats them as extremely valuable collectibles, it is believed that his collection is as big as six Sharingan pairs, and a single Mangekyō Sharingan pair, although he won't betray where he took them.