Additional Enchant

From what I heard it doesn't show on the weapon's stats, but that doesn't mean it isn't there; that needs to be tested.

ランダムボックス産のピアシング付きエンチャントの中には、ランス以外の武器に貼り付け可能な物もありますが、 元々ピアシングが付いていない武器にピアシングを付けても効果を発揮しません。 （ソードアートオンラインタイアップの35層、48層、56層、67層ESが該当）

Rough Translation: Something about Random Box (i.e gachapons) producing Enchants that increases Piercing Level and can be put on weapons outside lances. However, it will not take into effect if the weapon does not originally have piercing. (Applicable Enchants from SAO such as 35th/48th/56th/67th Floor ES)

Source

(Late Reply) I also forgot to mention it wasn't in the piercing modifiers, but there should be a note saying it is conditional