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.
Just doing a Cupid's job
Unexpectedly effectful
Give in to puppy eyes
It's made with love
Receive your punishment
"Save" Serra
Finally your aim paid off
Together in the Ferris Wheel
Get Serra into your bed
Find the helpless Mitsuki
Go back to Heaven
A friend always helps
Mitsuki's flawless plan
Get Mitsuki's Ending
Get Serra's Ending
Achieve the Harem Ending