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