Daimyo Koumei - Level Cap Build

Flexible Mods

Aura Slot - Flexible with anything that suits your loadout.

Exilus - Can use [Primed Sure Footed], although there is a decree that provides knockdown immunity, hence why I don't have it on. Cunning Drift for more range, Power Drift for more ability strength.

Augur Reach - [Rolling Guard] is one of my go to options for even more sustainability. Replace with an ability strength mod if using a subsume that relies on strength.

Fleeting Expertise - This is a personal preference. Primed Flow is an option.

Arcane Aegis - I like to run Molt Augmented when I'm using a subsume. Use whatever arcane suits your loadout.

Helminth

There are 2 Helminth set ups I like to run with Koumei.

Kumihimo is the subsume slot.

Sickening Pulse - This is used to make 4 deal more damage. Replace Augur Reach with an Ability Strength mod, preferably Precision Intensify as Sickening Pulse doesn't use strength.

Breach Surge - Use a strength mod, preferably [Umbral Intensify]. Swap [Augur Reach].

Archon Shards

1 Yellow Casting Speed
1 Green Corrosive Stacks
1 Violet [Equilibrium] Effect
The rest are flexible and can go with more Casting Speed, Corrosive Stacks, [Equilibrium], or whatever you feel like putting on.

Gameplay

Activate Omikuji ASAP and then Omamori ASAP after that.

For airborne challenges, bullet jump into the air and aim glide.
For sliding challenges, bullet jump into the air, aim glide and slide while gliding. This way you wont need to find slopes around the map to slide on.

Loadout

Anything goes, decrees make your loadout strong af anyway. I would recommend weapons with different primary elements for easier challenges, however it is not compulsory. You can also use [Cedo] as the alt fire launches a [Glaive] that procs the primary elements.

Use mods that have [Condition Overload] effects.

You can mod your weapons with corrosive to get that Archon Shard stack. However, if you are doing long runs, it would be better to use viral instead as some of Koumei's decrees provide corrosive damage.

My Loadout:
I mainly use Sickening Pulse subsume.
Cedo Prime - easy elemental challenges. Koumei's priming also increases its damage output.
Ocucor - auto aim makes some challenges easier.
Harmony - Expedite Suffering in a weapon. Stack up heat procs using [Ocucor], prime with skills and heavy attack.

Enjoy.