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