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