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