Bloodstained: Ritual of the Night - Zangetsu Boss Fight 2 & Zangetsuto Sword
Miriam faces Zangetsu in a boss fight for the second time in the Oriental Sorcery Lab, and wins the Zangetsuto Sword, required to cut down the demon Gremory. To reach the Oriental Sorcery Lab requires both the Invert Shard and the Aegis Plate body armour, to get past the spikes at the top of the Dian Cecht Cathedral area.
The Aegis Plate can be found by going to the Towers of Twin Dragons teleport, then to the lift and riding it all the way to the bottom, and using the Invert ability on entering the first room on the right.