I/O absolutely, does exist. Very weird VN to evaluate, but i'll give you my feelings: I didn't really get super invested until near the end of E route, so I enjoyed the primes more than the main game. It has pacing issues and the fighting is boring as hell (I hate it and skipped it 80% of the time). But the ideas are really good and I absolutely love the sense of unreality of the whole work. That's probably this game's best strength, in my opinion, and is why it's worth reading.