Im playing Shinden Horiuchi. Do all my Spell cards always count as Items, like when they e in my discard pile?
They are both Spells and Items while they are “yours”. That means “controlled by you,” which requires them to be in play. They are not Items while in your deck, discard pile, or hand. Bringing a Spell into play does quality for Reactions to playing an Item, however, such as the one on Shinden Horiuchi itself.