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