Support Items are usable during battle only. They are a one time use item, and you may not use more than one item at a time. They are independent from Special Items and thus can still be equipped even if Item is set to off. Support Items have no influences in-battle, but it has an effect on the aftermath of the battle.

All Support Items are AP items buyable from the Antiques Dealer, but some can be obtained as reward from musou board, or randomly get crafted instead of what you want to craft. There is also a chance that you may get some of these as an item reward from descending Kunlun Mountain.

Item AP Cost After battle Effect
Blacksmith's Sash 30 Slightly recover Weapon Durability.
Buddhist Scriptures 30 Honor gained increase by x1.5.
Chun Qiu Annals 30 Domestics gained from quests are doubled.
Confucian Classics 75 Honor gained is doubled.
Craftsman's Sash 15 Weapon Durability will not decrease.
Ginger Potion 60 Lieutenant Deed increases by x1.5.
Pearl Powder 60 Increase Lieutenant Affinity easier.
Seven Star Sash 60^ Some items found will be of higher quality.
Warring States 100 Items gained in battle will be kept even if you lost (same as novice difficulty).
Warrior's Scroll 30 Weapon usage will increase by 2 instead of 1.

^: Also obtainable by getting 30 stamps.