Rhei Of Paradise

Set on a paradise island hidden away by a company known as the Rebuilding Humanity Effort (RHE).  RHE has been trying to help progress human evolution by using existing traits from various species to build a stronger human body.  As its initial tests were on bovine traits and the production of an optimized human-specific food (Human milk); the island is also rather abundant in... female endowments.  You are unknowingly the friend of a woman employed by RHE, and now after years of loose contact she is reaching out to you, to invite you to this paradise for one day to see the sights and the many mammaries.

This CYOA is more of an experience than a straight story- there is no scenario in which you can win or lose.  You can pick where you go for morning, midday, and afternoon, and there is a re-read option built in to explore the many paths.  There is 34 endings, 4 Grand endings that require multiple normal endings to unlock, and a single Almighty ending for the few who actually manage to unlock all other content.

For those looking for a saucier experience, there are transformation sequences to be found and a few lewd moments, but for the most part this CYOA is considered more of a 'happily ever after' of transformation.  This is what their transformations have done to their lives, and the paradise created in its wake.  There are some scenarios which will fork your path without your direct choice- which items you interact with, who you choose to talk to before, etc- but I tried to make it so there is no better or worse option.  You will never really miss out on anything because of a choice, you'll just get a different scenario.  Some test subjects are found through Rare Encounters- and each of these has a different conditional trigger; the links to these are marked in red so you know that the option isn't normally supposed to be there.

And for those who cannot stand open ends... there is a Canon Ending hidden in there.