A handwork of Soushuu/Hikoshirō Hiromitsu, bestowed by the second shogun Hidetada to Date household. This sword was taken from said household in the postwar period and is now in a private collection.
According to Tokugawa Records, on day 21st of the 11th moon (lunar calendar), the 6th year of Genwa Period (1620), this sword was granted to Date Tadamune by Tokugawa Hidetada as the reward for finishing the construction of stone walls surrounding the Castle of Edo. From Date's side, in the document Datejikekiroku, there is an identical record. In Kensou Secret document, the bestowal was said to happen during the 10th month (lunar calendar). Previous ownership before Hidetada is unknown.
This sword can't actually be called Date Masamune's sword. According to the records, this sword was granted to Date Masamune's son, Tadamune. However, there is also a theory that states the stone wall construction was done in the name of Masamune and Tadamune only received the reward as Masamune's proxy.
Originally classed in game as a Tachi until 2015/07/22.
Some fanworks depict Ookurikara with Shokudaikiri Mitsutada and Tsurumaru Kuninaga. This is due to Mitsutada being owned by Date Masamune, and Tsurumaru being taken from a shrine to the Date Clan around 1716-1736. These three, together, are known as Dategumi in the fandom.
On his necklace, the Sanskrit character "kan" can be seen. This letter is said to represent the Shingon Buddhist deity, Fudo Myo-O (不動明王), otherwise known as Acala Vidyaraja.
The dragon on Ookurikara's arm, Kurikara, is said to be a representation of this deity as well.