Here is the full list of all 21 Misao: Definitive Edition achievements. It takes around 4-5 hours to unlock all of the achievements on Windows.
Clear Truth with the female protagonist.
Clear Truth with the male protagonist.
Free Kurata in the Truth route.
Give Misao some coins
Clear the main game with the male protagonist.
Clear the main game with the female protagonist
See the bad ending.
Find the message in the back of the laboratory.
Encounter Hanako.
Play the piano.
Save Kudoh.
Jump off the rooftop.
Talk with Library multiple times.
Get a whiff of a toilet.
Have a meal.
Check your key items.
Hide in a cardboard box.
Refuse to help Yoshino.
Read the diary in the library.
Read "The Lazy-Eyed Ranger."
Make a quicksave.