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