Here is the full list of all 26 Magical Diary: Horse Hall achievements. It takes around 15-20 hours to unlock all of the achievements on Windows.
You can't go home again.
You became a full member of the Rose And Wasp.
You maxed out your Weird.
You maxed out your Cute.
You retrieved the elusive stuffed bunny.
You maxed out your strength.
You broke your oath and lost your magic - for now.
You had an escort for the May Day Ball.
After a year locked in the school dungeons. Nasty.
You refused to attend any classes!
You maxed out your Blue Magic.
You maxed out your Red Magic.
You maxed out your Green Magic.
You maxed out your White Magic.
Too many demerits ended your school year.
You made it through the school year!
You maxed out your smarts.
Someone has locked lips with you.
Oops! Accidentally married.
You maxed out your Black Magic.
You maxed out your Stress.
You won the election for class treasurer.
You received detention
You received five detentions in one game.
You maxed out your Merits.
You helped Ellen form a school conspiracy