Here is the location of every fiend of the game:
1) Matador; Location: Great Underpass of Ginza. You can NOT avoid this fight, so you can't miss him.
2) Daisoujou; Ikebukuro (East Zone). After speaking with the leader of Mantra there will be a new demon close to the entrance of the city who speaks of a fiend, after talking with him go to the east zone of the city.
3) Hell Biker; In the Highway that leads to the Kabukicho Prison
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- You'll need to finish the 1st and 2nd Kalpa to continue; MAKE SURE you watch the cut-scene in the entrance of the 3rd Kalpa</li>
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4) White Rider; Close to the Terminal of Asakusa
5) Red Rider; Close to the Terminal of Great Underpass of Ginza
6) Black Rider; After completing the Obelisk, go back to the hospital, he'll be waiting in the room 204B of the Annex Building 2F.
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- Finish the 3rd Kalpa</li>
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7) Pale Rider; After hearing Futomimi's prediction about Yoyogi Park, go back to the Asakusa terminal and go north, then enter the first door you find that leads west.
8) The Harlot; Complete Yoyogi Park, then go back to Shibuya and exit to the world map, go north and enter Yoyogi Park by the West Entrance, she appears in the north area of the first screen.
9) The Trumpeter: In the entrance of Yurakucho Station.
You HAVE to defeat them in this order.