Theoretically you can achieve the Perfection with just 50 Bushido but...
You get 5% (Bushido/10, rounded down) when you hit and loose 25% bonus when you miss. So you hardly be able to keep Perfection bonus.
p.s. 120 + 80 = 200, this is why 80 is a magical number.
120 archery, 80 bushido, 200 points for special move mana cost reduction