Items

Items can be bought, picked up, and used by the protagonist throughout the game. They can be stored in Dimensional Boxes and sold at the Tem Shop in Temmie Village.

It seems that some weapons and armor come in "sets" (bandanna + glove, tutu + ballet shoes), probably meaning to signal about the other humans that fell down like Frisk did, their belongings now scattered. The battle with Flowey displays items that are thematically similar to these sets during the souls' interference (knife, glove, dancing, writing, cooking, gun), further suggesting this theory.