A little one sided but I couldn't see how the samurai could get close enough to melee.
Trust me, had they passed their activation rolls, it would have been a quite different outcome. Also, the terrain didn't help the shogunate forces at all: if the two cavalry squads could have run side by side one of them would have been able to arrive to close combat and probably destroy an infantry unit. Anyway, most Chosu casualties came from arquebus fire, so maybe you're right nonetheless.