Like the original game and NieR: Automata, Nier Replicant ver.1.22474487139… has several endings that are accessed by continuing from the same save file. Ending A is obtained by completing the game normally and will provide a Clear Data save file. Accessing this save file will allow you to advance the story.
Again, complete everything as usual to obtain Ending B. To access the next ending, you need to have collected all 30 weapons along with having unlocked the first two endings. Once this is done, access the save file again and play up till the final boss. Defeating it will unlock a new boss and provide two choices when it’s defeated. Go with the top choice for Ending C.
Access the save file once more and this time, select the bottom choice at the same boss fight for Ending D. While the original game concluded here, Nier Replicant ver.1.22474487139… actually has another ending. Once Ending D is completed, you’ll have to start a new game with a new name and save file. You’ll be in the Aerie and see Kaine on the ground. Head on over to her and from there, new events will unfold. Complete everything to see Ending E.