Board Thread:Questions and Answers/@comment-36381084-20180729175447/@comment-36471509-20180805175712

Befriend Papyrus (if you didn't do so), befriend Undyne, and go to the CORE. At the entrance, Undyne will call you and ask would you can deliver her love letter to Alphys. Deliver the letter. After the date, go to the True Lab and True Pacifist will occur.