I looked into the profiles. The "Danmaku" listed in the Peashooter's profile isn't really Danmaku, more like a directed barrage of attacks. A shockwave or even Gouketsu stepping aside would get around that. This would in theory make this an easy win for Gouketsu. However, the Peashooter's other abilities wouldn't make it too easy, especially with Spawnables (items). Because of this, I think it's easy for Peashooter to turn the tide against Gouketsu. Granted it's kinda annoying to worry about abilities stuffed into external pages (especially Physiology pages that assume a "one size fits all" ideaology), but still.
I feel a lot of what the Peashooter has, Gouketsu doesn't exactly have a counter to, so I feel the Peashooter wins this match.