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