Hey DelPonte, you have no idea how I feel happy about what you said about the story!
Did you played the game on physical cartridge?
Yes there are alternative endings... if you do 100% on collectibles you will got different choises to do and more explanations from the final boss, and if you do 0% on the collectibles AND you never upgrade your gun and armor you have another post credit sequence... (in that case you can still collect the shield and upgrade it to make everything more simple).
No, I played the digital version.
So happy to hear that! Because at least one of the endings might break players' hearts... Actually, I've beaten the game twice. The first time I didn't collect some items, so I didn't do 100%. Then I saw information about several endings and beat the game again, this time collecting all the items, I did 100%. But somehow the ending was the same... :( Although I really got more explanation from the final boss.