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