Shirosakura

Shirosakura (白桜（しろざくら）), meaning White Cherry Blossom is the legendary sword of justice.

Appearance
Shirosakura has a clear crystal like appearance. (Though in the movie it has a blue crystal like appearance.)

End of the World
The Shirosakura is first shown mounted on the head of a phoenix statue inside the Royal Garden as Athena showed Hayate the sword. Informing him that the Shirosakura had the power to rival the Kurotsubaki and that it was the king's sword used to carry out justice and only someone special could pull it from the statue.

Later, after Hayate left the the Royal Garden, after responding to her cries for help, Ikusa finds Athena sitting alone on the stairway asking her if she called him. After hearing that she cannot leave the Royal Garden, Ikusa tries to reassure her that he would get her out, causing King Midas to manifest behind him before making an attempt to attack. While avoiding the attack, Shirosakura breaks from the statue and flies towards Ikusa. Catching it he takes Athena and cuts off King Midas's right arm and then continues to attack him relentlessly forcing King Midas to open a pathway to outside the Royal Garden.

After getting her out of the Royal Garden, Ikusa places the Shirosakura next to Athena's unconscious body as she slept for a year. After being left with the sword Athena eventually places the Shirosakura within Machina's body after he became her butler.

Golden Week Arc
Near the end of the Golden Week vacation, Ginka extracts the Shirosakura from Machina's body and gives it to Hinagiku to use to assist Hayate in his fight against King Midas. After King Midas's defeat, Hinagiku keeps the Shirosakura and uses it as her main sword.

Trivia

 * Prior to the tankōbon versions release, the Shirosakura's name was originally the Hokuou.
 * This could be a reference to Hakuo Academy, since it was built over the Royal Garden, where the Shirosakura was originally placed at prior to its construction.