Among the many points of interest you can find in Onimusha: Way of the Sword are the Oni Gates. These special locations take you to optional areas of the Oni Refuge. Once there, you'll need to solve a small puzzle to unlock access to new special abilities. Keep in mind that this section only covers optional Oni Gates, not those tied directly to the story, with the exception of the first one, which is connected to unlocking new abilities and must be activated to progress.
This Oni Gate is activated automatically as part of the story during A Strength in Refuge.
It's located inside the well in the compound south of the fields, where you'll need to activate an Oni Glyph.
This is the Oni Gate on the Kamo River island. It's activated using the Oni Glyph on the Kamo River island; follow the instructions there to learn how to reach it.
As soon as you enter, shoot the block to move it out of your way. Then turn back and head down the steps. Beneath the ruins, you'll see another block you can shoot. Doing so will raise it and create a bridge that lets you continue across the ruins.
Continue until you reach a dark mass to unlock new enhancements, along with several materials as a reward.
You'll find this Oni Gate after activating Eastern Kyoto Oni Glyph #23, in the northeastern corner of the map. It's inside the well immediately west of Oni Glyph #22. Once inside, activate the Glyph and wall run across the first wall. As soon as you land, turn around and look for the block you need to shoot to move it.
Before wall running across the second wall, shoot the block directly ahead of you.
You can now wall run across the second wall and reach the cloud of darkness.
