Reina was born into the Natsumi Clan, and grew up in the Natsumi Mansion as she would spend countless hours training, preparing to take over the leadership of the Natsumi family but on her 17th birthday, her family is attacked by Jungle who demands the power of the Black King, who is able to heal the Sword of Damocles and bring the Kings together as one.
Jungle reveals to Reina that she is the Black King and that the aura that wafts from her is the proof. Jungle tells her that the powers of the Black King will reveal itself on her 17th birthday and Reina decides to give up the power in order to stop her family from being murdered, but she is told that if she gives up the power, it would be the end of her.
To stop Jungle from obtaining Reina's powers, she is trapped in ice making her fall into a deep sleep. 3 years later, Reina reawakens from the spell as the Black King and finds out all her family members were slaughtered except for her two loyal bodyguards. Reina vows to avenge her family and decides to stop Jungle who plans to release the Slate's entire power and propel the evolution of mankind.
"When 'colors' mix, they become muddy and messy. But when they all blend together, the final result is the color that wins against all others... Black. I am the Black King"