Justin Bieber and Sofia Richie spent her 18th birthday together in Los Angeles.

After enjoying alone time in Japan earlier this month, Bieber and Richie were believed to have split as he was spotted with model Bronte Blampied in London, but after returning to The States, Bieber quickly returned to Richie and enjoyed a fun night out with her last night.

"Justin was doting on Sofia the entire time, caressing her back and playing with her hair,” an eyewitness at Doheny Room in West Hollywood, Calif. revealed to Hollywood Life on Thursday. “They were both super flirty with each other. At one point he serenaded ‘Happy Birthday’ to her. They were with a group of friends and had a table in the upstairs lounge area.”

While Richie was spotted earlier in the evening at The Nice Guy, she and Bieber reunited after what appeared to be a dinner with friends and arrived to The Doheny Room at 10 p.m.

“They had a really good time,” the source explained, "Everyone was having fun and laughing.”

In other Bieber news, fans of the singer were recently led to believe he may be heading back to Instagram after quitting the social media platform earlier this month after Selena Gomez accused him of cheating. Although Bieber didn't exactly say he was considering a return, the tweet below has many thinking he will soon be back.

For more on Bieber and Richie's romance, check out the video below.

Tags: Justin Bieber sofia richie