There are over 160 characters each with roughly 10 video files for just the repeat sex scenes and around 10+ pictures for each character. The game adds lots of content when it adds a character. If a character is living in the city and you know their residence then you can visit them and fuck them in repeatable non story interactions, you can also talk to them which can open a new quest or story event. There are over 160 of these characters with over 10 videos on average that is 1600+ video files and these are just the generic none event based repeatable sex scenes. I mentioned this in multiple posts. The videos are not 2 or 3 second loops they are often 20 seconds or more as well.
Play the game and you will find the story. You have to READ the story otherwise you wont know what is going on or what to do next or when to met people. Why is the 13 gigs? because it has a whole story, over two chapters with loads of events.
The game is 13 gigs because it has 13 gigs of content, seriously I already posted it had dozens of characters each with 10+ videos each for just repeatable non event content and the video's are mostly compressed .webm format. It is 13 gigs because it has 13 gigs of content. The archive is 13.1 gigs and the loose files are 13.2 gigs there isn't any compression to be done as that is a less that 1% compression rate. And if people don't have the internet resources to download 13 gigs they shouldn't play the game because it is ONLY going to get bigger as time goes by. It shouldn't be a mystery why the game s 13 gigs.