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?

The imperial family collapsed during one night by the basilisk, the summoned beast of darkness which was summoned by the cursed princess, Fleta. “If there is a next life, then… Can I really be your younger sister?” If I had approached you a little earlier, would it have been different from now? The last time everyone regretted it, the time miraculously returned to 6 years earlier. If this is the second chance we've been given.