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