Here is the full list of all 45 AI: The Somnium Files achievements. It takes around 20-25 hours to unlock all of the achievements on Windows.
Day 4: Monday - Cleared Ota's Somnium.
Collected 100 "Appendix" files.
Finished Iris's investigation.
Day 5: Tuesday - Cleared Iris's Somnium.
Cleared the shooting event at the Warehouse District with no misses.
Day 4: Monday - Cleared #89's Somnium.
Day 3: Sunday - Cleared Iris's Somnium.
Cleared the shooting event at the Kumakura office with no misses.
Enjoyed a fulfilling chat with Kagami.
Day 4: Monday - Cleared Iris's Somnium.
Day 3: Sunday - Cleared So's Somnium.
Cleared the shooting event at Golden Yokocho with no misses.
Day 2: Saturday - Cleared Mizuki's Somnium.
Day 1: Friday - Cleared Date's Somnium.
Found 1 hidden item in Somnium.
Obtained all other trophies.
Day 5: Tuesday - Cleared Mayumi's Somnium.
Day 6: Wednesday - Cleared Date's Somnium.
Day 5: Tuesday - Cleared Boss's Somnium.
Day 5: Tuesday - Cleared Hitomi's Somnium.
Day 6: Wednesday - Cleared Saito's Somnium.
Found 6 hidden items in Somnium.
Found all hidden items in Somnium.
Finished Ota's investigation.
Finished Mizuki's investigation.
Finished Annihilation Route investigation.
Finished the final investigation.
Asked out the receptionist to Atami.
Cleared the shooting event at the Sejima residence with no misses.
Cleared the shooting event at the Sagan residence with no misses.
Confronted Iris with the evidence with no mistakes.
Confronted Ota with the evidence with no mistakes.
Confronted So with the evidence with no mistakes.
Confronted Hitomi with the evidence with no mistakes.
Collected all the "Persons" files.
Collected all the "Dream Album" files.
Checked absolutely everything in Boss's office.
Admired the Sagan's stereo equipment.
X-rayed the Mermaid.
Kept your cool and did not shoot Saito.
Discovered the marriage of the yakuza and the nurse.
Saw This Man twice in Somnium.
Had Aiba wear the basket and the pot in Somnium.
Saw three autographs of crazy customers in Somnium.
Almost got cursed by Adorabbit in Somnium.