Kanshou and Bakuya

Kanshou and Bakuya are twin swords forged from the same ore that were originally owned by Second Prince Seien but given to Sixth Prince Ryuuki when Seien was exiled from the palace.

Years later, the sword Kanshou was given to Shi Seiran to protect Kou Shuurei and To Eigetsu when Seiran is ordered to escort the pair to Sa Province as the new governors.