How should I explain this.... this is a huge part of gameplay.
The Pink orb(印) is what gives the Weapons, Shields, and Amulets the various abilities. Sort of like a add-on modification.
Every Equipment has a set amount of pink orbs it can have, and you can't put in more than the max number.
Pink orbs can be added by synthesizing.
Some Pink orbs can level up, but it can only gain exp. when it is the 'Base Pink orb"(The innate one) or when the Weapon or Shield is a specific one.
Pink orbs that have been synthesized doesn't normally gain Exp.
Pink orbs can be also in other items, like Spell Cards or Potions.
Pink orbs can be classified by Weapons-only, Shields-only, and others.
Weapons-only pink orbs have red Kanji, and abilities include increased damage to certain types of enemies, ability to break terrain, and other things that usually happens when attacking.
Shields-only pink orbs have blue Kanji, and abilities include reduced explosion damage, automatic counter when attacked, and other things that usually happens when attacked.
Other pinks orbs have white Kanji, and can be either Amulets-only or can be synthesized in more than one type of equipment.
I can rant more about this because it is important, but I fear that it will become too long.
And to answer the question :
A lone Pink orb as an item can be either obtained by one of Shou's special ability to pull out a non-Base Pink orb of a equipped item, or putting an item in 消化のスキマ(Sukima of Digestion) and breaking it by throwing it at a wall. The Pink orb as an item can be used to just synthesize the Pink orb to a Equipment. Choose the Pink orb, choose 使う(use), then choose a Equipment to synthesize the Pink orb.
