Bullet hell shooter. Set in a world resembling Japan's Taishô period, the people have discovered the powerful Blood Swords, the titular Akai Katana. Requiring human sacrifices to unleash their immense destructive power, they have been used by the empire to crush neighbouring countries. However, all the bloodshed has made some of the swordsmen reconsider. With the powered up swords at their disposal, this small band of rebels now fight back against the tyrannical empire. (wikipedia)