A possession-type demon weapon of the Black Demon series wielded by Guren Ichinose. The blade presumably takes on the form of a black katana with a glowing crimson red streak that is outlined down in the middle portion of it. It increases Guren's physical abilities significantly and, when calling upon her name, it also increases his own power tremendously.
-- From Wikipedia
Replica of Guren Ichinose's "Mahiru-No-Yo" katana (trans. Midday's Night) from the anime series Owari No Seraph. 106 cm. Carbon steel with zinc fittings. Comes with wooden sheath. Black and red streaked blade. 1.25kg.