Know the story behind the character
Known as Shuichi Minamino in the Ningenkai (Human World), he is actually the reincarnated legendary fox spirit Kurama in the Makai (Demon World), and his fame stretches far and wide across its borders. The powers that he could wield always involve plants, and his favorite weapon is the "Rose Whip": a whip covered with thorns derived (of course) from a rose. As a youko, his preference for weapons varies. During his four hundred years as a youko(fox spirit), his purpose in life was to hunt for knowledge and power, but a hunter managed to critically wound him. He tore his soul from his body in desperation, and fled to the Ningenkai: a place safe enough to allow him time to recuperate. He found Shiori Minamino: a kind and gentle human who was carrying a child in her womb. Kurama took over the child's body and got reincarnated in the process.
Having taken on another form, Kurama was renamed Shuichi Minamino (spelling varies). Being a youko at heart, he planned at first to regain his powers and to leave his human family at age fifteen. But being blessed with a human heart, Kurama learned to love his human mother above his own life, and would gladly trade it for Shiori's safety. An instance occured during his childhood wherein he fell along with a few plates after trying to reach something from a high shelf; Shiori quickly shielded his head from hitting the floor, but her arms got harshly wounded by the porcelain shards of the shattered plates, rendering them scarred for life. Seeing the great sacrifice Shiori went through for him, Kurama's love for his human mother grew extensively. Afterwards, he became the perfect son for Shiori, and did almost nothing to displease her.
When he was fifteen, Shiori came down with a sickness that no doctor could identify or cure. Being desperate for a cure, he joined a group of thieves (Hiei and Goro)and stole the three Reikai (Heaven) treasures. One of those treasures was the Mirror of Utter Darkness: a Mirror which granted wishes in exchange for the life of the holder. After gaining possession of the Mirror, Kurama disbanded from the group and took the Mirror with him. Yusuke Urameshi, a Reikai detective, was on the search for the three items, and he encountered Kurama during his hunt. Kurama confronted him and told Yusuke his present situation, and asked Yusuke to return the Mirror for him when he's done. He wished for his mother's recuperation, and then willingly let the Mirror slowly drain his life force. But Yusuke intervened and offered his own life, reasoning out that he couldn't bear to see a mother lose her child.
After a while, Kurama regained consciousness and quickly ran to his mother. The Mirror had decided not to take either of their lives, and fell into Yusuke's possession after the incident. Shiori was, of course, well and cured. Kurama, then, with Hiei, also became a Reikai detective as a means for Koenma (son of Enma Daioh, manager of the Spirit Detective Agency) to keep an eye on both of them.
Among all his friends, Hiei seems to be Kurama's closest, though a lot of people see this as material for shonen ai and yaoi :). The two of them understand each other deeply, though Kurama has many other friends.
Hiei and Kurama's first meeting was, more or less, a violent one. When Kurama was still ten years old, a girl from his class (named Maya) had confessed that she loved him and got attached to him. Afterwards, while Kurama was walking with Maya along the street, Hiei suddenly appeared and accused Kurama of being a spy of Yatsude, a youkai (demon) who had managed to enter the Ningenkai. Hiei was hunting Yatsude for his own reasons. Kurama and Hiei fought, and Kurama decided to take the fight elsewhere lest someone else got involved or hurt, leaving Maya on the street to wonder about what she had just seen. But a few kids being possessed by Yatsude's spies kidnapped Maya and brought her to Yatsude.
Meanwhile, during his fight with Hiei, Kurama saw blood spilling from Hiei's clothing, and shortly afterwards Hiei fell. Kurama brought him to his room and healed his wound, then waited for him to wake up. When he did, Kurama asked Hiei his name, and Hiei reluctantly gave it. When Hiei left through the window, the phone rang and a spy of Yatsude told Kurama about Maya. Alarmed, Kurama quickly joined Hiei in his search.
When they arrived at Yatsude's location, they encountered him and quickly avoided his blows. But when Yatsude held out a child's bloody foot, Kurama became enraged and charged with a sword he had created from a leaf in his hand. Hiei joined him and with teamwork, they managed to kill Yatsude in two slices :). Kurama saw Maya and erased her memories of the incident, then carried her on his back. He said he will never have anything to do with her afterwards. Hiei, then, asked Kurama his name, and Kurama gave it willingly.
To find out more about Kurama during the YYH series, here's a link for further info.