SPSF-03 Tsubaki, the Demon-Sealing Swordsman by Mei Mitsuki

Hundreds of years ago, Omuro Tsubaki, a descendant of the demon slayer who sealed away the Demon King Gouten, was on a journey to prevent the Demon King's resurrection. A demon, a vassal of the Demon King, appeared before Tsubaki, but Tsubaki, clad in crimson armor and wielding the sword Suzaku, passed down through her family, defeated the demon. However, the Demon King's vassal, Makisuke, resurrected the Demon King Gouten. Defeated by the Demon King's overwhelming power, Tsubaki is captured and tortured. The Demon King challenges Tsubaki to one last battle. As a descendant of the demon slayer, Tsubaki mustered all her strength and gripped her sword. Will Tsubaki be able to seal the Demon King...? [BAD END]