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