When this card is Normal Summoned, you can: Special Summon 1 “Shiranui Spectralsword” monster from your hand or Deck, also you cannot Special Summon monsters for the rest of this turn, except Zombie monsters. If this card is banished: You can draw 1 card, then discard 1 card. You can only use each effect of “Shiranui Squire” once per turn.
The Shiranui archetypes main strategy is banishing their own monsters and triggering their effects, usually this is done by other Shiranui monsters as effect cost. Because Shiranui Squire is able to Special Summon another Shiranui from the deck, its most common use would be for Synchro plays.