Here is the full list of all 25 Seduce Me the Otome achievements. It takes around 1-2 hours to unlock all of the achievements on Windows.
Be Baptized by Angels.
Start your Adventure with Diana.
Obtain True Power.
Get Proposed to by Andrew.
Be Eaten Alive by Diana's Pit Beast.
Go To Paris with Naomi.
Prove Your Love to Suzu.
Fight Malix Yourself.
Give Damien his Humanity.
Find Harold Anderson's Magic Books.
Obtain True Freedom.
Share some Cake with Matthew.
Accept Sam for the Man he is.
Preview the start of Seduce Me 2: The Demon War!
Witness Simon's Transformation with Diana and someone special...
Kiss Erik under the Moonlight.
Get Proposed to by James.
Turn down sex, but keep your true love.
Unlock the Second Set of Bloopers!
Dodge Malix in time.
Get Shot in the head by Malix.
Unlock the First Set of Bloopers!
Impress the House Party Guests.
Prologue Completed!
Rename the Main Character.