Sera d'Coeur

Sera is the princess from Azarus, a small island kingdom. Shortly after her birth, the King and Queen met with the Zoldyck family and formed a contract. In exchange for being raised with the family of assassins, when she comes of age, they can pick a son for her to marry and therefore have a direct connection to the royal bloodline. They formed this contract due to receiving a warning that their kingdom would soon be invaded by a more powerful country. In order to keep her safe and unknown from the world, Sera was sent away.

The head of the Zoldyck family decided that Sera would eventually marry Illumi because they want Killua to become the next head of the household. Being the same age as Killua, Sera and Killua grew up together and quickly became very close. However, Sera was quickly taught that Illumi was her master and she was his servant and had to obey Illumi's every order. Luckily, Illumi mostly decided that Sera should follow Killua around. Only Zeno, Silva, Kikyo, and Illumi are aware of Sera's true heritage.

As a member of the royal family, Sera possess a unique ability that is inherited. According to the legend of the Azarus kingdom, the first king married the Queen of the demon realm. As the queen of the demons, all other demons were forced to obey her. As the family line continued, all members of the royal family possessed the skill to summon demons and form a contract with them. Sera is also able to do this upon reaching the age of ten. Upon her tenth birthday, she recieves a letter from her birth parents given to her by Silva. In it explains her birthright and how to summon a demon companion. She initiates the ritual and summons Akira, a kistune who vows to protect her.

When Killua and Sera are twelve, Killua decides to escape the family lifestyle and runs away to take the Hunter's exam with Sera in tow. It is then that Sera experiences an adventure that will change her life completely.