When decoded properly from Cyrillic (Windows-1251 or KOI8-R), the text translates to: What this is:
Summer of Love is an adult-themed visual novel or dating sim.
This specific link is for a step-by-step walkthrough (manual/guide) for version 1.1 of the game.
It looks like you’ve come across a title that’s suffering from some (often called "mojibake").
Socigames is a well-known Russian-language community and hosting site for these types of games and their associated guides.