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