Here is the full list of all 18 No One But You achievements.
Good end
A starry sky or Chinatsu, which is more beautiful?
Bad end Yui
Good end Yui
Second bad ending Yui
Bad end Megumi
Good end Megumi
Megumi why?
Received the greatest honor, Megus panties!
You went on a date with Megumi!
Kissed Ryo
Why do that to Yui?
You have achieved the most important achievement in the game, The Lap Pillow with Ryo!
Bad End
Good End
You met a white haired girl on the roof
Good job, you started the game...