Scarlet Soul Manga Vol. 02 GN

Two sisters, Lys and Rin Shirano, watch over the Hundred Altar Gate that maintains balance between the worlds with the help of the Sword of a Hundred Souls. But one day, Lys disappears suddenly, and the sacred sword she left behind reacts oddly to a mysterious phenomenon. Accompanied by the demon Aghyr, young Rin sets out on a quest to find her sister through a kingdom that's once more under threat...