Here is the full list of all 55 Summer Meetings achievements.
Kissed at least four girls during a playthrough
Things are getting weird
Someone got scared of you
Faced two alternatives
Decided to break all bonds except one
Just... why?
Decided to return, but changed your mind at the last second
Lost a place to stay TWICE
Got the worst ending
Lost a place to stay
Ran to someone but didn't speek
Seen all 15 festival events!
A difficult situation turned a bit awkward
That's not good...
Seen all epilogues
Seen Reina's epilogue
Seen Akari's epilogue
Seen Yuka's epilogue
Seen Shiori's epilogue
You broke up in style!
That's not how a festival should be...
What did you think would happen?
Started dating Shiori
Seen Mei's epilogue
Started meeting with Mei
Stuck with one girl from the start
Got back together with someone
You were just curious what happens, right?
Visited the oceanarium
Pushed someone away
Started dating Yuka
Rejected a confession
Someone confessed their love at festival!
You thought it guaranteed a happy ending?
Went to a concert
You've been caught
Admitted your disloyalty
Started dating Akari
After rejecting a confession, asked her on a date
Started dating Reina
Parted in peace
Learned something
Four heroines met
Went to the sea
You did not forget!
Learned the reason of breakup
Activated #Help in settings
Finished the game before it really started
Did you thought she'll appear again?
Seen an ending
She never had a chance
Not nice, is it?
You don't know what a promise is, do you?
Started the game
Will it lead somewhere?