I Raised My Younger Sister Beautifully

When Princess Fleta, who has been mistreated her entire life due to being born with a curse, summons the basilisk and destroys the palace, Princess Cezanne regrets that things could have turned out differently if someone had been by Fleta's side. So when she miraculously finds herself six years back in time, she is determined to take Fleta under her wing and fill her baby sister's life with nothing but joyful light. Will Cezanne be able to dispel the darkness inside Fleta and rewrite the ending? (Source: Tapas)