Even though Emma (Jennifer Morrison) said that all-important "I love you" to Hook (Colin O'Donoghue) at the end of Once Upon a Time's fifth season, don't expect it to be entirely smooth sailing going forward.

Fans of "Captain Swan" were delighted to see Emma profess her love for Hook while not under any sort of life-or-death scenario. But Once Upon a Time showrunners Edward Kitsis and Adam Horowitz have warned fans not to expect a "fairytale" moving forward.

"We pick up pretty directly from where we left them at the end of last season, where for the first time Emma professed her love without the duress of a life-or-death situation," Horowitz noted to TVLine. "Of course, life-or-death situations come pretty quickly on our show, so that will change."

Kitsis added, "No relationship is a fairytale. So if people are expecting no drama, we hope that they will enjoy what we are showing."

The new season is set to also feature more backstory for Hook, with some surprises ahead for the audience.

"He's pretty much the same Hook," O'Donoghue teased previously to Entertainment Weekly. "Now that they know it's true love with Emma, they're trying to figure out how to navigate being together. We might find out a few things about his past." Horowitz added, "There is more of Hook's past that we delve into and some surprising secrets that have been harbored."

Meanwhile, Emma will be focused on helping Henry (Jared Gilmore) with the Land of Untold Stories. In the premiere, Emma finds herself developing a "mysterious side effect" as she goes against Hyde (Sam Witwer).

Once Upon a Time season 6 premieres Sunday, Sept. 25 at 8 p.m. ET/PT on ABC.

Watch the promo for season 6 of Once Upon a Time below: