Eiyuden Chronicle: Hundred Heroes' immense party recruitment should come as no surprise — it's in the name. But that does lead to some issues when you're swapping out your active party members, namely when it comes to optimizing gear and Runes.
How To Change Gear And Runes For All Party Members In Eiyuden Chronicle: Hundred Heroes
To save you from constantly swapping party members in and out of your active crew just to change their gear, there is an easier way. You'll need to head to the Item Warehouse once you've unlocked the castle HQ. The warehouse can be found on the main floor, to the left of Ymir and the planning development desk. Head to the left side of the floor and speak to Sumire.
Select "Gear Prep" where you can then choose to either "Switch Gear" or "Change Runes". Both options allow you to view all of your recruited characters and adjust the gear of each one. It also allows you to equip each character with gear and Runes you've stored in the warehouse.
This means that unless you're hoping to change Runes and Gear on the fly, or in random towns, you can safely store your unused equipment in the warehouse and free up your own inventory space.
Sadly, this option still requires a lot of manual work when it comes to choosing the best equipment for each ally. There isn't an option to automatically apply the most optimal gear, so you'll need to handle that yourself.