Heya! Okay, so I assume you did reach ending 5 too? It's intended for the player to see all the endings to get the 'whole' story, but ending 5 should explain all the questions. If you'd rather check the spoilers first, I have a post about the endings 5 and 6 [here], but it's spoiler heavy.
I am glad you enjoyed the game, and I hope you'll like the sequel too! :D The demo is out, but the rest of the game is on hold as of now, but the prologue should give you some answers as to MC's future post ending 5.