Was an event drop until 2016/03/15. He can be obtained through Kebishii drops.
The first sword, along with Higekiri, to have more than one entry in the citadel logbook.
Like his brother, Hizamaru had several names throughout history:
Makuragami (枕上, on the cushion): the first known name of this sword. It comes from the theory that the Emperor of Japan ordered to forge two swords using the iron of an exactly halved naginata. The blacksmith Mōfusa forged Hizamaru, and Kokaji Munechika forged Higekiri, which measured three sun less than the other sword. The first blade was named Makuragami due to the alleged honest use of the material, and reached a privileged position over Munechika's sword.
Hizamaru (膝丸, knee cutter): the sword was renamed after a cutting test (tameshigiri). In that period it was usual to use criminals and dead bodies to check the quality of the blade, and this sword managed to cut from the neck down to the knee of the victim.
Kumokirimaru (蜘蛛切丸, spider slasher): the name changed again when Minamoto no Yorimitsu (Raikō), who was suffering from a sudden illness, slashed a shadow that approached him in the midst of a feverish delirium. It turned out to be the influence of a Tsuchigumo.
Hoemaru (吠 丸, howler): both swords Hizamaru and Higekiri came to Minamoto no Tameyoshi's hands, and he changed their names after a night when he noticed that the blades were making noises and grunts. Hizamaru sounded like a snake and Higekiri like a lion's cub.
Usumidori (薄 緑, light green): Minamoto no Yoshitsune renamed this sword again because it reminded him of the Kumano mountains. It is now the official title of the sword, which might have been the main inspiration behind his brother's depicted inability to remember his name, as he is no longer known by the one he used to have.
His constant striving to earn his brother's attention and affection was likely inspired by the relationship between their historical owners. Hizamaru was owned by Minamoto no Yoshitsune, who in life had a lot of respect for his brother Yoritomo, who happened to be the owner of Higekiri.