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