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