Here is the full list of all 13 Hatoful Boyfriend: Holiday Star achievements. It takes around 5-6 hours to unlock all of the achievements on Windows.
Get to the end of the short episode "Pigeon Shrine Visit".
Read all of the King's picture book.
Get to the end of the short episode "The Day the Night Slept (After After)".
Get to the end of the short episode "Preliminary Inspection".
Get to the end of the short episode "Albert's Secret".
Get to the end of the fourth episode.
Watch all of the Radio episodes.
Get to the end of the short episode "Midnight Attack of the Nightmare".
Get to the end of the short episode "Legumentine's Chronicles".
Get to the end of the third episode.
Get to the end of the second episode.
Get to the end of the first episode.
Watch one of the Radio episodes.