Here is the full list of all 26 The Quintessential Quintuplets - there are Memories of a Quintessential Summer achievements.
Unlocked all Achievements.
Viewed the normal ending for the "Nakano Ichika Route."
Viewed the good ending for the "Nakano Ichika Route."
Viewed the normal ending for the "Nakano Nino Route."
Viewed the good ending for the "Nakano Nino Route."
Viewed the normal ending for the "Nakano Miku Route."
Viewed the good ending for the "Nakano Miku Route."
Viewed the normal ending for the "Nakano Yotsuba Route."
Viewed the good ending for the "Nakano Yotsuba Route."
Viewed the normal ending for the "Nakano Itsuki Route."
Viewed the good ending for the "Nakano Itsuki Route."
Viewed the normal ending for the "Raiha Route."
Viewed the good ending for the "Raiha Route."
Viewed the normal ending for "All Route."
Viewed the good ending for "All Route."
Created a schedule.
Selected someone for cooking duty.
Cooked something up.
Activated Futaro Support.
Experienced a game over.
Someone collapsed.
Viewed the tutorial.
Viewed all endings.
Completed the entire SCENE GALLERY.
Completed the entire CG GALLERY.
Completed the entire SOUND GALLERY.