Equipped creature gets +3/+1.
Whenever equipped creature dies, return that card to the battlefield under your control if it's a Samurai card.
When Oathkeeper, Takeno's Daisho is put into a graveyard from the battlefield, exile equipped creature.
Equip {2}
Oathkeeper’s second ability checks whether the card’s creature type is Samurai, not whether the creature was a Samurai when it left the battlefield.