Here is the full list of all 13 Short Stories Collection of Class Tangerine achievements.
Reach all endings in My Girlfriend wants to lose weight
Complete My Girlfriend wants to lose weight 20 times (any ending counts)
Reach any good ending in My Girlfriend wants to lose weight
Reach any bad ending in My Girlfriend wants to lose weight
Finish Story The ghost is very cute
Finish Story The ghost is not very cute
Finish Story Invisible Lover
Finish Story Last 12 Hours
Finish Story Butterfly
Finish Story One Day Girlfriend
Finish Story It is Spring Festival so the monster is very cute
Finish Story May be Halloween so the ghost is very sprouting
Finish Story 11+11