Mr. Caribdis, you have created a masterpiece! This is the best AVN there is. I love the story, it has everything. A bit too much comedy for me, but you implemented it very well. Different routes/endings are well constructed; playing the secret ending route was depressing(an effect that lasted for a couple of days even after finishing the game), but that's how it's supposed to be. The epilogue for the harem ending was extremely well done.
I love all the characters, those girls are great! However, I also appreciate the fact that a lot of men are present in the game. Some of the other AVNs have literally no male besides the protagonist and I just can't help but think "Come on mate, I can handle a man being on screen. Surely the story would make more sense and be overall better if you included some. You never stated that men were extinct and the main character was the last guy on Earth". Anyway, good job with that.
As for visuals, overall the game is very satisfactory. The only thing I can fault you for is all the texture clipping, but hey - you are one guy, doing the entire game by yourself as a side-job, plus this is your first project, it's completely understandable. Honestly, with how enjoyable Once in a lifetime is, I really don't mind it. There is a great variety of outfits(that fit the circumstances they are worn in), the girls change hairstyles - these are factors that give you points in my book. Animations are great. Angles are well chosen. While I don't usually care for different points of view during sex scenes, as with many other things, you did well in this department.
The level of English is good(especially compared to a lot of other AVNs), however there was still some amount of errors. I'm sure I'll be playing the game in the future again, I could write them down and send you corrections.
Eternum. I will be completely honest with you: I am really not a fan of the "VR game within a game" concept, especially if we are talking about an adult visual novel. It is very unappealing for me. However, I owe it to you and your first game to at least try it. Which I will definitely do, albeit only when the game is finished. Because it is your game, I want full experience of a completed product, so I shall wait until it's done before I play it. By the way, is your name a reference to a certain... individual... from Greek mythology?
This is one of my favourite game games of all time and I don't mean just within the AVNS.
Thank you for creating Once in a lifetime!