Kentaro, the Smiling Cat is a rare Legendary Creature — Human Samurai card from Betrayers of Kamigawa (BOK), collector number 13. Current market price: $2.23 (foil $17.09), TCGplayer market prices via Scryfall.
Bushido 1 (Whenever this creature blocks or becomes blocked, it gets +1/+1 until end of turn.) You may pay {X} rather than pay the mana cost for Samurai spells you cast, where X is that spell's mana value.