Here is the full list of all 21 East Tower - there are Takashi achievements. It takes around 0-1 hour to unlock all of the achievements on Windows.
You've unlocked all of the Achievements!
You've unlocked all of the CGs!
You've got the Love Ending!
You've cleared the Love Stage!
You've cleared the Past Stage!
I feel stupid, knowing I was only worried because of him
You've cleared Stage 4 and done an excellent job!
You've got the Normal Ending!
You've cleared Stage 7 and done an excellent job!
You've cleared Stage 6 and done an excellent job!
You've cleared Stage 5 and done an excellent job!
It seems that I'm his first love.
You've cleared Stage 4 and done a good job!
You've cleared Stage 3 and done an excellent job!
You've cleared Stage 3 and done a good job!
You've cleared Stage 2 and done an excellent job!
You've cleared Stage 2 and done a good job!
You've cleared Stage 1 and done an excellent job!
You've cleared Stage 1 and done a good job!
You've got the Bad Ending!
You've cleared the Prologue!