Here is the full list of all 16 Sakura Cupid achievements. It takes around 0-1 hour to unlock all of the achievements on Windows.
Achieve the Harem Ending
Together in the Ferris Wheel
Get Serra's Ending
Receive your punishment
Finally your aim paid off
Get Serra into your bed
Get Mitsuki's Ending
Mitsuki's flawless plan
A friend always helps
Go back to Heaven
Find the helpless Mitsuki
"Save" Serra
It's made with love
Give in to puppy eyes
Unexpectedly effectful
Just doing a Cupid's job