Act 4 is the fourth and final act. In this version of the game, everything seems to be back to normal with the exception of Monika's absence. If the player restored the character file of Monika after starting a new game it will prompt a message saying "Please stop playing with my heart. I don't want to come back." and it will delete the character file. The protagonist decides to join a club by his own volition and, encountering Yuri and Natsuki's friendly disposition to one another and also Sayori, convinces him to stay and fill the quota needed to make the Literature Club official.
After Yuri and Natsuki leave the room, Sayori talks to the protagonist but revealingly the player. She comments how she is now club president, and therefore, she knows everything that has happened. Sayori then decides to pick up where Monika has left off in Act 3, but Monika is revealed to not quite be gone and deletes Sayori before she could do anything else.
Monika concludes there is no happiness in the Literature Club, primarily because one has to be president, and being one gives the character a revelation that drives them to insanity. Monika then decides to erase the whole game, but before she does so, she presents the player a song she saved called "Your Reality." It plays as the credits roll until the final end screen that depends on what the player has done before Sayori's suicide.
- If the player did not save-scum throughout the game, the CGs presented during the credits will be deleted and some appearing gray during so. The note left behind is Monika's notice that the Literature Club has been disbanded and how she still loves everyone.
- If the player save-scummed and looked at all the CGs before Sayori's suicide and continued the game normally then, Sayori won't attempt to continue where Monika had left off in Act 3 but rather thanks the player for being thoughtful about making everyone happy. Sayori then decides to keep it this way by bricking the game but keeping the character files so this present can remain catatonic and everyone happy. The note left behind is a "thank you" message from the developer.
Afterwards, any interaction with the game will pop up an error message prompting the player to reinstall the game in order to play again. An offline alternative is to delete "firstrun," which allows the player to perform a hard reset.