Here is a simple guide for you to download and install R18+ patch. enjoy the new patch.
How to Download
You have it.
Nice, next step
How to Install (Step-by-step Tutorial)
4-Search the game directory :
Disk\SteamLibrary\steamapps\common\Summer~Life in the Countryside~\Summer~Life in the Countryside~
6-The uptade apply automatically
7- Wait and when is finish close