Doki Doki Literature Club Plus! (EU)

To unlock the side stories, you'll need to write poems for Sayori, Natsuki, and Yuri on three different playthroughs of Act 1. More specifically, I believe you'll need to view the two different CGs you see in the story itself when you write a poem for each girl. I don't believe the third CG for each one matters, but it may be safe to go ahead and view them anyways. Basically you'll be following the same process as getting the good ending. The first time you see the poem mini-game start, save your game. Each day write a poem for the same girl, which will unlock their first two CGs if you only focus on the same one. Until the day of the festival starts. At the start of this day, load up the save from the first poem mini-game and repeat the process for each girl until you've seen each of their cinematic scenes once.

For the third CG's you can get Yuri's and Natsuki's by helping them with the festival over the weekend. For Sayori's you have to

Keep in mind that you MUST load the first mini-game up before you reach the moment when

Once you hit this point you won't be able to load the save, thus making it impossible to view each cinematic if you haven't already.

Once you have done this, you should have all six side stories. They are called (in chronological order) Trust, Understanding, Respect, Balance, Reflection, and Self-Love. There are two parts to each side story, and you have to get through the entirety of them all. You can use the skip option to get through all the dialogue you haven't seen. If you want to actually read the stories, feel free, but just be aware that these are long and somewhat redundant. Using the skip option usually make each story end in less than thirty seconds, plus you can always re-watch them if you're interested.

Finishing all six pairs of side stories unlocks a seventh, one-part story called Equals. Play this one as well, and when it's over you should have your achievement. Happy hunting!