VENGEANCE: LAST NINJA ASSASSIN

A boy saw his parents killed in his house by a group of Yakuza. Because they didn't want to kill a boy of six, they dumped him in the middle of a virgin forest on the skirts of Mt. Fuji, where nobody lived but one. The boy was saved by an old man who was a professional assassin. Boy had lost all memories, but the darkest angers welled up from deep inside him whenever he tried to think of the parents. Old man sensed his anger, decided to take him under his wing, and trained him as a Ninja assassin.
Boy wanted to give up a hard training million times though, whenever he was beaten, the anger forced him to keep moving, and reached Satori at a tender age of sixteen - time to move back to a society. Old man gave him a new name; Shinji Nakamori: New-born In-the-forest.
Shinji was initiated by Akemi who was Kunoichi, a female Ninja, on the first night in town. Akemi thaught him not only how to live with the people, but also the art of seducing. Thus Shinji became not only a superb killing machine, but also a formidable womanizer - he could seduce any woman, put her under hypnosis during sex, called Dragon King's Coupling, extracted all information without her knowledge.
Shinji recovered all memories when he was ready, avenged the deaths of his parents.