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