some tips on what everything means would help, i don't speak Japanese very well, and i read even less 
I've been playing the monster prince game for a while, and I picked up a few things along the way.
Areas and combat:
The basic gameplay consists of you defending different areas of your domain with your monster army, with the castle or throne room being the most important (farthest to the right).
You assign troops to garrison each area, the enemy randomly attacks each area.
Not all areas are available in the beginning, after between ten and twenty turns you will see enemies attack places you can't reinforce, once defeated by succesfully attacking them, these become additional parts of your domain.
In the case of the above, or if the enemy heros destroy all monsters guarding an area, then the area is taken over.
If your garrison does not cause the heros to flee, and there are any left after time runs out, then the area becomes contested.
If either area contestment or loss takes place, you no longer receive gold from that area, and reinforcing or attacking it becomes very expensive.
Area improvements can be built, the top one allows more troops to be stationed there, and the second controls the % of elite troops in an area.
Economy, Gems, and Upgrading
After defeating a group of heros, you will gain gems based on how many losses there were (both sides) and time taken (longer is better). At the beginning of each day, you will gain gold based on the areas you control and purple % bonus you get from getting blowjobs from the princess.
Gems can be used two ways, to upgrade your troops, and magic spells.
Magic spells can be used up to three times per day and once per battle, with red being a damage spell. Right click during battle to use.
If you are using a red spell, you should do so at the beginning of the battle unless you are going for losses, as it will often wipe out the hero army or cause them to retreat.
Note both the regular and elite troops can be upgraded. If you don't have the cash or stamina to upgrade the %s of elites in each area, don't upgrade them until you do.
You might want to keep the troop and spell upgrading to the minimum needed to beat the heros, for two reasons; You will earn more gems from more losses, and in new game plus you carry over all your gems and money, but do NOT carry over ANY upgrade bonuses. (Except for the bottom choices for the purple demons, for some reason.)
You can convert gems from smaller ones to bigger ones or vice versa, but this uses stamina and until you get towards the end game and need the big gems, not recommended.
H-scenes
You can have sex with the princess for various bonuses, purple giving a bonus to gold each day as represented by the purple %.
Scenes with other women are unlocked as you play, but I have no idea how they do so, although No 8 seems to always be unlocked no matter what.
You cannot capture the female heros through gameplay.
Other
Playing on "normal" is not recommended until you are an expert. I was using cheats for infinite gold and later stamina, and I actually had a hard time with some of the later battles because I didn't realize I would need such large garrisons. Its easy enough at first, but then the enemy starts throwing waves of 500 enemy heros at you per attack late in the game, and it gets expensive just replacing garrisons, much less reinforcing contested positions, which almost always happens with large waves as at a certain point no more heros or monsters will spawn until the ones in the field are killed. Use the red spell...it helps.
After normal comes nightmare, a form of new game +. If you have played DOOM before, then you might know what to expect, if you haven't, well let's just say the nightmare is for the demon king, not the heros.
Cheat engine works well with this game.
Enjoy.
