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