Alright, comprehensive review time motherfuckers:
Jesus Christ where do i even start?
First an foremost, if your looking at the itch.io page wondering whether or not you should download the game, DO IT
Once in a lifetime is one of the most complete adult games I've ever played before, its got everything. Heartwarming romance, great sex scenes, an amazing sense of humor, genuinely scary horror sections, and quite literally the best plot I've ever seen before in a visual novel.
Its not just your typical "Boy wakes up and builds a harem in a week" type games, its clear how much effort was put into the story and background of the world, and the multiple endings are all great. Except for the secret one. That one still eludes me xD
Eternum is gonna be in development for at least a few more years, having played 0.3 to completion and having 0.4 ready to go after i post this i am very excited as to what will happen next!
I really do hope there is a least a little bit of crossover between the two games, maybe the OIAL MC could tutor Eternum MC in how to handle having a harem, and maybe a little bit on the occult too.
God bless you Caribdis you glorious bastard, and I am so excited to see what you come up with next!