Equipment
Weapons, Armor, Accessories, and Guardian Spirits can all be equipped separately between Samurai and Ninja Style.
Weapons
Each weapon has unique Attack values, special effects, Break (your ability to break the enemy's stance), and Block (affects how much Ki you lose when blocking attacks) stats. Furthermore, as you continue to use a weapon, your familiarity with it will increase. As familiarity gets higher, the weapon's special effects will be enhanced, and the Amrita you receive when offering it will increase.
Armor/Accessories
Armor and accessories all have unique weights, Base Defense, special effects, Toughness (affects Ki damage and how easily you are staggered), and elemental resistances. Armor is split into light, medium, and heavy categories, which roughly indicate weight and damage reduction. The heavier your armor, the slower your movements, and the more Ki attacking and dodging will consume.
Guardian Spirits
Depending on your Guardian Spirit, the resulting enhanced player stats, special effects, and usable Guardian Spirit Skills change. When you destroy a Crucible Spike, the special effects and Guardian Spirit Skills available to you increase.
You can also enhance your Guardian Spirits via "Manage Soul Cores" in the Shrine menu.
Soul Cores
The boost to Attack and Defense, special effects, and available Onmyo Magic differ with each Soul Core. Additionally, the effects gained from a Soul Core change depending on whether it is in the Yang or Yin position in the Onmyo Box.
Note: Soul Cores can be obtained by defeating yokai. Upon obtaining one, pray at a shrine and purify the Soul Core to use it.
Rarities
Items have different rarities: White < Yellow < Blue < Purple.
With higher rarity comes stronger special effects and a higher familiarity limit.
Item Shortcuts
Item shortcuts can be set via "Equipment" or "Items" in the Main Menu.
By setting certain items to your shortcuts, you will have immediate access to them during missions. Items that may be useful include: Life-restoring elixirs; throwing stones, which can be used to draw the attention of a locked-on enemy; items used to recover from status ailments, such as antidotes and antiparalytic needles; and so on.