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