Samurai School in Nakano

Get this Quest from the Shinjuku Hunter Association after completing Kill the Black Samurai / Kill Yuriko. Accept this quest to make it active then exit to the city map. From Shinjuku Station, head west until you reach the barrier then follow the road north. There should be a tall building there, near the toxic swamp which you can enter. Save your game and you’ll find Marici inside. Choose to fight her when you’re ready.

LV47 Marici

Marici has two press turn icons and will attack first using Agidyne. She doesn’t seem to have any elemental weaknesses so bring Demons that has defenses against fire and/or gun attacks. Her HP seems to be around 2500. You can also use Tetrakarn to deal multiple damage to her by reflecting all shots of her Myriad Arrows attack. Aside from that, she’s not a particularly hard enemy, as long as you exploit her attacks against her. Defeat her to complete the Quest. You'll also be able to fuse Marici in the Cathedral of Shadows.