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 male protagonist.
Clear the main game with the male protagonist.
Save Kudoh.
Hide in a cardboard box.
Play the piano.
Jump off the rooftop.
Read the diary in the library.
Free Kurata in the Truth route.
Find the message in the back of the laboratory.
Have a meal.
Clear Truth with the female protagonist.
Give Misao some coins
Clear the main game with the female protagonist
See the bad ending.
Encounter Hanako.
Refuse to help Yoshino.
Get a whiff of a toilet.
Read "The Lazy-Eyed Ranger."
Talk with Library multiple times.
Check your key items.
Make a quicksave.