1 - Remove the Depth of Field and default AntiAliasing Settings

Replace Engine.ini with the included file in:
C:\Users\*YourUserName*\Documents\My Games\Octopath_Traveler\Config\WindowsNoEditor

2 - Make sure you have the latest version of Reshade.

Target the Octopath executable and choose the 
OctoCleanTraveler preset ini file during install.

The preset uses the following:
ArtisticVignette.fx
Levels.fx
PD80_03_Shadows_Midtones_Highlights.fx
PD80_04_Contrast_Brightness_Saturation.fx
PD80_04_Selective_Color_v2.fx
qUINT_sharp.fx
Unsharp.fx

Note: If you do not like the sharp pixels toggle off qUINT_sharp for a softer image.