Here's Why Kourtney and Kim Kardashian Got Into a Fight on 'Keeping Up With the Kardashians'

By now you've seen the explosive fight between Kourtney Kardashian and younger sister Kim Kardashian West in the trailer for Season 18 of Keeping Up With the Kardashians.

In Thursday's Season 18 premiere on E!, viewers found out exactly what caused the fight, which saw Kim repeatedly slap her older sister. And it's all to do with work ethic.

At the end of the episode, Kourtney, Kim, Khloe Kardashian, and Kylie Jenner talked about youngest sister Kylie Jenner not being able to walk in a fashion show because of an illness. Kim said, "If I were on my deathbed, I would still show up."

Kim implied that Kourtney and Kylie don't have the same ethic as her and Khloe, adding, "Mom is so used to me and Khloe going on our deathbeds... ." Kendall protested that she works hard, too, but Kim countered, "No, you'll get anxiety and it's hard for you."

Kim reiterated to Kourtney that "mom is so used to... me and Khloe, whenever, if we're sick... you don't care about stuff."

Kourtney took offense to Kim's comments, saying, "You act like I don't do s***. You have this narrative in your mind." As Kim tried to interrupt, an irate Kourtney said, "No, no, no, I will literally f*** you up if you mention it again."

Things got more heated as Kim tried to laugh off the escalating tension. Kourtney said, "Literally, shut the f*** up and don't laugh like that."

"Honestly, change the narrative in your mind. I work my f***ing ass off," Kourtney told Kim. "But also, if I didn't want to work my ass off and I wanted to be a stay-at-home mom, that's f***ing fine, you f***ing literal..." Kourtney said, throwing a water bottle at Kim.

The argument turned physical as Kourtney grabbed Kim and said, "I will literally f*** you up," as Khloe tried to break up the fight.

"Don't ever come at me like that," said Kim, "I swear to god, I'll punch you in your face." Kim then tried to land a punch on her sister, followed by a kick. Khloe continued to try to separate the pair.

Kim then followed Kourtney to the door, telling her, "Don't ever dig your nails into me like that. How old are you?"

Kim then landed two slaps on her older sister. Kourtney then said, "How old am I? How old are you?"

The episode ended on that cliffhanger — viewers will need to wait to until next week to see how the family feud resolves.

Kim and Kourtney Kardashian fight
Kim and Kourtney Kardashian fight. E!