Higetsu, Nezumi Blade Artist

Rat offering (You may cast this card any time you
could cast an instant by sacrificing a Rat and paying
the difference in mana costs between this and the sacrificed Rat. Mana cost includes color.)
When Higetsu, Nezumi Blade Artist enters the battlefield, Rats you control gain bushido 2 until
end of turn. (Whenever this creature blocks or
becomes blocked, it gets +2/+2 until end of turn.)