What's Kim Kardashian really doing in Tokyo? Full details

Kim Kardashian is reportedly in Japan to cheer on boyfriend Sir Lewis Hamilton at an F1 race for the first time.

The 45-year-old reality star brought three of her four kids- Chicago, 9, Psalm, 6, and Saint, 10 - along with her to Tokyo, where Lewis will race on Sunday, March 29.

"She was at the Las Vegas Grand Prix last year but kept things quiet because their relationship was still in the early stages," an insider told The Sun.

"Now they are a proper couple and she will be cheering him on with the kids. They’ve been hanging out together in Tokyo and have been having a great time," added a tipster.

Kim and Lewis were seen grabbing dinner together in Tokyo on Wednesday, March 25.

Recently, an insider revealed to People magazine that the SKIMS founder and the F1 star have "more than just a casual connection."

"It takes a lot to capture Kim's interest and she's definitely intrigued," the confidant continued.

The source added, Lewis is "just an easygoing guy with great energy. Her family likes him and Kim's very into him. They are both busy with their careers, but see each other as much as possible."