Here is the full list of all 17 Every Summer Holiday - there are BL (Boys Love) Visual Novel achievements.
Accept Jason's Confession
Accept Eddie's Confession
Reject Jason's Confession
Reject Eddie's Confession
Finish the Bug-Catching Mini-Game
Cook a Good Meal
Stay as Friends with Jason
Stay as Friends with Eddie
Only Date Jason
Only Date Eddie
Date Both Eddie and Jason but Their Affection Is Low
Date Both Eddie and Jason but Their Affection Is High
Reach Max Bond with Grandpa
Reach Max Bond with the Innkeeper
Reach Max Bond with the Waitress
Reach Max Bond with the Doctor
Reach Max Bond with the Stylist