Damn! I feel bad for Dev because of the storm, at least the good news is that he was fine and all the works are still be continue and in the last stage of completion. Can't wait to see how the next update will be like, holy damn 1.2GB of new content alone are pretty big and show how hard work and generous Snats are. I tipped my hat to him, he got all my respect even more so than before
That size is because the game is essentially screenshots made from Koikatsu Studio.
A lot of VNs with characters made with Koikatsu characters do it the same way, that's why their sizes is so big.
For example, the first pajamas party with Jaiden contains 283 pictures and video with them mostly being pictures.
That event alone is 74MB in size and that's the heavily compressed version!
It's very different from most other games as they use models in game and only save those animation. Those take up way less space as the only thing different is the position and the orientation of the models.
This is also why you probably will not see our characters wear different clothing in the same event. He has to redo the whole event, taking new screenshots with the other clothing. It's a lot of hardwork, but it is one of only ways that is accessible for indie devs without a lot of game making knowledge.