Ashigaru's ability is that you go second on the first fight. In other words, you'll play first in the second & fourth rounds when Ashi's one of your 4.
Leaders work through all the fight even if attacked/blocked by stop.op.ab. cards. Ashigaru is different , his skill makes you play second in the opening round. That doesn't sound that impressive but you still get a 8/6 card , best leader's stats and one of the nicest cards around (esp the looks;))