Our order of battle:
The Terrain:
Generally open. The path towards the enemy is open plain, although in our deployment area there's a marsh of limited importance. To our left is a patch of forest which we could *probably* use to mask our approach of our left flank to a degree - should we choose to advance that way, anyway. It is hilly beyond this forest. The Chinese have a hill on their side and will likely deploy artillery there.
The Enemy:
We are facing the Ming Northern Army. It is materially well-equipped but spiritually lacking. It is safe to say that their infantry, despite their combined arms tactics (musket regiments with light spears + regimental guns) is inferior to ours, and in melee they will not last long.
We will probably be facing substantial amount of cavalry and must prepare for this. The horsemen who defend China against Mongol incursions are ironically Mongols themselves, so there will be no question of their spirit or skill. They favor the bow, but can use the sword just as well. In constrast, our mounted Samurai are equipped only with lances and swords, as use of the bow on horseback has fallen out of favor among our fighting elite.
The Chinese are fond of deploying field guns. In such open terrain we are going to be pelted by them. We can take a defensive stance if the enemy chooses not to move, but if he does not deign to sally out, we must bring the fight to him.
Us:
We are the Japanese. Our army is the result of over 100 years of civil war. Our men are therefore better than the hopelessly underfunded Ming government forces and unlike them, all sport standardized, mass-produced armor and effective matchlocks. Our adoption of pike-and-shot tactics means that our spear ashigaru units are close-order foot, and will be terribly disordered in rough terrain such as forests. If we should enter such terrain, we should let our sword-armed foot lead the way.
Our Samurai still fight one-on-one with the enemy like the honorable fellows they are, and therefore have poor cohesion. They might get carried away while pursuing routers and get surrounded as a result. We must prepare for this.
As for our horsemen, our cavalry arm must be the worst in East Asia. We can expect them to hold in melee but Ming cavalry will probably evade their charges and counter-fire with their bows.
Standard Japanese tactics during of the period have an emphasis on melee. Musket infantry would close in, weathering enemy fire, to let loose a volley that would hopefully disorder the enemy ranks and make them more vulnerable for the Japanese charge.
The Plan:
That's up to you. What the hell do we do, Holla Forums?