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