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