These are both basically the same thing. In one of the walkthroughs here it is on page 30, but it took me some time to understand, so I'll try to summarize. After you are finished with the Angel Moe (Moe Amatsuka) storyline, 4 of the girls in your villa gain a new stat (you can check it ingame by clicking on the character picture in the character page). You need to raise this stat to 40 by doing scenes with them in the villa (the massage room, classroom, infirmary), some of those scenes gain you 2 points, but most gain one. The only consistent non-rng way to get a point is training room in the basement. After you get 40+ points with each girl, you need to get to empire building and talk to Moe and iirc there are some more scenes you need to go through before you are ready for the welcoming party.
Honestly the machine translated walkthrough here is a pain in the ass, but I somehow managed to get it done, so if you maybe go trial and error after the 40 point mark, you should get it eventually.
