So I don't know where else to put this but I'll be giving a mini guide for the game so ya'll don't have to suffer like me.
I'm assuming you want to go through the story naturally and not jump straight into the gallery. This also assumes that you got tired of waiting for translators and kagura, so you'll be using a partial+AGTH or machine translator.
The story itself is straight forward, you can always just go to the next newest location and you won't have an issue.
The lewd scenes are locked into two parts, pre and post first ending. Everything pre ending is straight forward enough to get. However, there is one missable scene that can screw you over. After defeating Douglas the 16 Shogun/General, wander around the top floor of Celis house at night. You'll get brought to the throne room and told you have to eff Douglas cause porn plot reasons. IF YOU MISS THIS OR SAY NO, THERE ARE NO MORE NEW SCENES POST GAME. After you effed him and clear ending 1 (some dude called Clarence), you will trigger the "nasty flag". This lets you do all the weird background animations and go around town nude at night fking people. It also opens 60-70% of the scenes in the game which are only available after the ending.
Honestly post game is where the real lewd scenes start, and everyone goes into turbo slut mode.
Everything else is straight forward and you can always go back for it so no worries on that front. I did miss a few minor scenes but nothing special.
If you want to access the secret room in the cg room, you need to download the attached file and put it in the same place as the exe file. The secret room lets you reset virgin, change lewd parameters and start NG+, though I warn you that all it does is let you keep levels and stats, not lewd stats. So basically its just cheat engine but legal.
AMA if you need help with a story trigger. I'm a big fan of GYU games and I spent hours finding the flags for scenes.