The single sold 621,000 units since its release on July 3, the highest first-week sales for a foreign artist ever, according to a news release on Tuesday from Oricon, the leading music industry statistics group in Japan.
Japan is the world's second largest music market.
The Korean megastars broke their own Japanese record of 455,000 sales for "FAKE LOVE / Airplane Pt. 2," released last November.
The new single features "Lights," a track sung and rapped in Japanese, along with Japanese versions of "Boy with Luv" and "IDOL."
A music video for "Lights" was also released last week.
The group's latest accomplishment comes on the heels of breaking a nearly 25-year-old record for best-selling album in South Korean history.
Map of the Souls: Persona sold 3,399,302 copies in their home country as of May, adding another entry for BTS in the Guinness Book of World Records. The seven-track album had been released just a month earlier.
The boy band -- consisting of members RM, Jin, Suga, J-Hope, Jimin, V and Jungkook -- has also managed to conquer the world of mobile games.
BTS World, a story-based simulation game for iOS and Android, hit the top of Apple's App Store charts in 25 countries within the first day of its release in late June.
BTS is currently in Japan on the final leg of their world concert tour "Love Yourself: Speak Yourself." The septet performed at the 47,000-seat Yanmar Stadium Nagai in Osaka last weekend and will finish the tour at the 50,000-seat ECOPA stadium in Shizuoka Prefecture on July 13-14.
The group will release a documentary film from the tour, Bring the Soul: The Movie, on Aug. 7, an "event cinema" release that will open globally for a limited run. Their previous film, Burn the Stage, already holds the event cinema box office record, pulling in 1.4 million viewers around the world over a handful of days in 2018.