Board Thread:Questions and Answers/@comment-35928801-20181115042720/@comment-37637755-20181127011322

You will get a Neutral ending on your first playthrough. However, after the neutral ending, if you meet the requirements of a True Pacifist Route (not killing anyone, befriending Papyrus and Undyne) then you will get the chance to reload your save file and complete the True Pacifist ending. Flowey gives you instructions and the game guides you where you need to go.