Chapter 18 (The Demon on the Mount) is the chapter's longest set-piece. Musashi clears the Mount Oe Castle Courtyard against a yokai-cult army. The climax is the Burai–Ifuu–Perfect Storm combination boss. Estimated 3–3.5 hours.
1. Chapter Overview
| Attribute | Value |
|---|---|
| Chapter | 18 — "The Demon on the Mount" |
| Estimated Time | 3 – 3.5 hours |
| Difficulty | Hard |
| Setting | Mount Oe castle courtyard, side caves, summit watchtower |
| Story Summary | The bardic troupe's confession implicates a yokai cult on Mount Oe. Musashi climbs to the mountaintop castle where the cult's leader prepares a Perfect-Storm ritual combining the Burai, Ifuu, and Rasho-gan essences. |
| Key Unlocks | Perfect Storm Soul Core, Sixth Enma Page, Moonshadow Talisman, Yokai Codex final entry |
| Recommended Level | 27 – 29 |
Chapter 18 ("The Demon on the Mount") is a 3 – 3.5 hours segment of the 22-mission main story of Onimusha: Way of the Sword. The structure, enemy compositions, and item placements below are based on the verified first-week launch state. Use the walkthrough checklist to track every encounter, item, and missable. Recommended for players clearing the chapter for the first time on Difficulty Mode II — the chapter scales to whatever level you enter.
2. Main Objectives
- Ascend Mount Oe via the eastern switchback path
- Clear the lower castle courtyard (8 Brutes + 4 Byakue)
- Solve the Flashing Void puzzle in the side cave
- Survive the watchtower gauntlet
- Defeat the Perfect Storm combination boss at the summit
- Recover the Sixth Enma Page from the cult leader's shrine
3. Walkthrough
Sections In This Chapter
Section 1 — Eastern Switchback
The eastern switchback is a winding mountain path. Eight Genma Brutes patrol it in two groups of four.
Take the shortcut through the bramble-arcs to skip half the patrol density. The shortcut saves roughly 5 minutes but bypasses the Headliner.nl document hidden in the patrol-sergeant's tent.
Section 2 — Lower Castle Courtyard
Lower courtyard: 8 Brutes + 4 Byakue officers + 1 Lantern Captain.
The castle walls funnel Brutes into a bottleneck. Use Marcellus Soul Core (Chapter 12) for a power-strike combo on the bottleneck to stagger groups without losing position.
Section 3 — Flashing Void Puzzle
The side cave has a Flashing Void — a void-rift that spawns and consumes Genma in 3-second cycles. Step through the rift at the right moment to enter the upper cave.
Timing is critical: the rift opens for 1 second every 4 seconds. Watch the central eye — it flashes when the rift is about to open. Step through on the second flash.
The cave also has a Hozuki pouch token #14 hidden in the Genma-archer's cache. Some patrols sit on top of the cache; clear them all to access.
Section 4 — Watchtower Gauntlet
The watchtower climb is split into three stages. Each stage spawns 4 Genma Archers that fire from above.
Use the Nue Soul Core (Chapter 9) wind-burst to stagger Archers across stages. The longest stage (Stage 2) has 6 Archers + a new towering Siege Genma Brute that drops a Hozuki pouch token #15.
Section 5 — Perfect Storm Combination Boss
The summit cult leader performs a Perfect-Storm ritual combining Burai, Ifuu, and Rasho-gan essences.
Phase 1: Burai (rhythm-synced musical blade) on the left. Parry on the third chime. Phase 2: Ifuu (ranged volleys) joins from the back. Deflect arrows. Phase 3: Burai and Ifuu merge into Perfect Storm — a single Genma-wraith wielding twin blades at the speed of light. Chain-deflect all hits to break the posture.
Section 6 — Cult Leader's Shrine
Recover the Sixth Enma Page from the cult leader's shrine at the summit.
The cult leader escapes through a portal mid-cutscene — a setup for Chapter 21's Dokyo final showdown. The shrine relic holds the Enma Page behind the central altar.
4. Key Items & Collectibles
| Item | Location | Effect |
|---|---|---|
| Perfect Storm Soul Core | Combination boss drop | Light-speed blade gauntlet ability |
| Moonshadow Talisman | Watchtower Stage 2 chest | +15% deflect vs ranged Genma |
| Sixth Enma Page | Cult leader's shrine | Hozuki Pouch upgrade piece (6/7) |
| Hozuki Pouch token #14 | Flashing Void cave cache | +1 pouch slot |
| Hozuki Pouch token #15 | Siege Brute drop | +1 pouch slot |
| Yokai Codex (final) | After Perfect Storm | Codex entry finalized |
| Sun-Dried Hozuki x16 | Courtyard reward | Crafting material |
5. Missables
- Sixth Enma Page — the cult leader's shrine only opens if you kill the cult leader before he escapes. If you let him escape he seals the shrine.
- Headliner.nl patrol-sergeant document — hidden in the patrol-sergeant's tent on the eastern switchback. Take the bramble shortcut and you skip the document.
- Yokai Codex final entry — examining the Perfect-Storm corpse locks the codex. Skip the inspection and the entry is locked until NG+.
- Hozuki Pouch token #14 — inside the Flashing Void cave, only accessible if you clear all Genma-archer patrols first. One un-cleared patrol and the cache is sealed.
6. Soul Farming Opportunities
| Location | Enemies | Souls / Clear | Respawns? |
|---|---|---|---|
| Eastern switchback clear | 8 Brutes | ~520 yellow | Yes (NG+) |
| Lower courtyard clear | 8 Brutes + 4 Byakue + Lantern Captain | ~1100 yellow | Yes (NG+) |
| Watchtower gauntlet | 4 + 6 + 4 Archers | ~780 yellow | Yes (NG+) |
| Perfect Storm combination boss | Burai + Ifuu + Perfect Storm | ~3200 yellow | Once per save |
7. Chapter Checklist
Track your Chapter 18 run below. Selections are stored locally in your browser and persist between visits.