Here is the full list of all 20 the 9th day achievements.
Another story pass.
Collect all CG.
Suzu line pass.
Mai line pass.
Saki line pass.
Maki line pass.
Appreciation mode all music listen once.
Watch ED for the first time.
Game time breaks through 20 hours.
Game time breaks through 10 hours.
Through the link in game to arrive at the official shop.
Through the link in game to arrive at the official blog.
Through the link in game to arrive at the official website.
Watch OP for the first time.
Prologue finish.
Save the game once.
Go through the whole game following the option order.
Pass Saki line again after passing Another story.
Occupy all archive places.
accomplish all above and get a platinum trophy.