This game is structured with Part 1 as the base game, followed by additional parts released as patches. Therefore, after purchasing each file, you will need to combine them into a single folder. The process is simple—please refer to the instructions below. 

1. Download the latest versions of Part 1 and Part 2.
2. Extract (unzip) Part 1.
3. Extract Part 2, then copy the all unzipped files (*.rpa) and paste them into the "game" folder inside the Part 1 directory. (Note: Paste into the subfolder named "game", not the main folder.)
   
4. If the game runs correctly, you're all set. (A new title screen and BGM will play.)

If Part 1 is not the latest version, it will not be compatible with Part 2.
The demo version, early access version, and other unofficial versions of Part 1 are not compatible with Part 2.

For comments and questions, please use Part1 community (consolidated). 
https://kujiranosenaka.itch.io/saimin-ippon-hypnoticthrow-part-1