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