Incredible game, amazing animations, after the first sex scenes you'll have to wait a while before getting any more and with how slow the transitions are that will take a while. But trust me it's worth it.
The room selection seems like a redundant feature as there was no point going anywhere that you weren't told to go to, this combined with the slow transitions really makes the game drag, and the dialogue selection isn't much better you may get slightly different dialogue but the outcome is always the same. Although I guess these issues make it all the more enjoyable when you finally get another sex scene.
I recommend using this guide to avoid spending ages checking rooms that have no content and are only designed to waste your time:
Sisters: Last Day of Summer Walkthrough Guide
Pros:
- Incredible sex scenes
- Beautiful girls
- Good story
- Good character development
Cons:
- Weird 3d scenes
- The slowest transitions I've ever seen
- The room selecting and choice mechanics
- Disappointing ending
Even with all the cons I still thoroughly enjoyed it, so I can't give it any less than a 5 star. Although if it were possible I'd give it a 4.5 star rating.
Story spoiler:
From what I gathered you are their brother suffering with a memory loss disorder that makes him forget everything after 14 days so they decide to keep this a secret as it's probably less stressful. A bit like people who suffer with dementia. You spend most of the game seeing things that hint towards this and then the game ends with no conclusion.