Kim Kardashian Sports Super Sheer Top at Justin Bieber Concert to Show Off 42-Pound Weight Loss

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The star-studded Justin Bieber concert at the Staples Center in Los Angeles on Wednesday night also turned out to be a Kardashian family affair.

Kim Kardashian West and her husband, Kanye West, attended the show after already taking in Justin's concert on Monday night, along with Kim's sisters, Kourtney Kardashian, Kendall and Kylie Jenner, and Kylie's boyfriend, Tyga. Wednesday night also marked Kourtney's second time seeing Justin in Los Angeles during his Purpose tour, after she was spotted hanging with the "Sorry" singer's mom, Pattie Mallette, backstage on Sunday night.

Rocking a completely sheer top and a tight-fitting black skirt, Kim looked incredible, flaunting her weight loss since giving birth to son Saint in December. On Monday, Kim revealed on her app that she's already lost 42 pounds, and has a goal to lose 28 more.

WATCH: Kanye West Excitedly Sings and Dances at Justin Bieber's Show With Kim Kardashian

Maciel / AKM-GSI
Maciel / AKM-GSI

The 35-year-old reality superstar posted a video on her app on Thursday, reminiscing about how she got in shape again after giving birth to her daughter, 2-year-old North, in June 2013.

"I look back at photos like this that kind of inspire me," she says, sharing a picture of herself looking slim in a pair of leggings and a sports bra. "I remember, 'I did it then, I can do it now,' and I have to be patient. This was, like, a year after I had North. It's still motivating to me."

Unfortunately, Kim didn't post any Snapchats this time around of Kanye's adorable dancing at Justin's concert, but 18-year-old Kylie did post plenty of videos of the sisters and their significant others goofing off at the Staples Center.

Kim, Kanye, and Kourtney all joined Justin at the Warwick lounge in Los Angeles following the concert, where they sat at a VIP table near the DJ booth and appeared to be in "great spirits," a source tells ET. Kim chose not to drink, the source adds, and the trio left at around 1:15 a.m.

"Justin was drinking and having a great time, hanging with his A-list friends and other VIPs," the source says. "Kim, Kourtney and Kanye kept a low profile and let Justin enjoy his special night."

Other celebs at the singer's concert on Wednesday night included his ex, Selena Gomez, and his label-mate, Tori Kelly.

WATCH: Justin Bieber's Mom, Pattie Mallette, Supports Him at Los Angeles Show Following Estrangement

Watch the video below for more on Kim's impressive post-baby weight loss.

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