Nero Crescent is a half-Saiyan, half-human descendant of Sephiroth who was trained by Vegeta to avenge the death of his ancestor. He is the older brother of Hirudo Crescent.
Nero was born in an unknown country south of Japan, the eldest son of Joshiro Crescent and Mikazuki Tsuki. His father had been a son of one of King Vegeta's scouting troops, which passed the Saiyan blood to himself and Hirudo. Joshiro was killed by Frieza during a spy mission prior to the discovery of the Dragon Balls, a few weeks after Hirudo was born. Nero, raised by his mother, used to be a fun-loving, hyperactive child. When he turned five his mother told him the story of how his ancestor, Sephiroth, had been killed in the crossfire of Madara Uchiha and Hashirama Senju's war in Konoha many years ago. Awed in pure shock at this revelation, Nero immediately lost his childhood innocence and became more serious, determined to avenge his ancestor's death no matter the cost. Vowing revenge on Konoha's warring clans, the Senju and Uchiha, Nero left home in search of a surviving Saiyan to teach him how to fight. He stole the legendary sword that was passed down from generation to his father, the very blade that had once been a valuable asset to Sephiroth himself. He nicknamed this the "Sword of Sephiroth" and set off. He eventually came across the infamous Prince Vegeta, who was reluctant to take on a student. After many efforts to convince him, Vegeta finally caved in and agreed to train Nero. Nero trained for many years, eventually coming to an advanced form of image training called, "Memory Training". This allowed Nero to fight those who had perished, consisting of his father, Frieza, and even Sephiroth himself. At the age of sixteen Nero left Vegeta and reunited with his brother, Hirudo. He took over a nearby country and renamed it "New Jenova."