She was 40.
According to The Japan Times, Takeuchi's 35-year-old husband, actor Taiki Nakabayashi, discovered her lifeless body in the couple's bedroom around 2 a.m. in Tokyo's Shibuya Ward on Sunday. Takeuchi was subsequently taken to a hospital where she was pronounced dead.
Tokyo authorities are investigating her sudden death as a possible suicide, though no suicide note was found.
For the past two decades, Takeuchi was a mainstay on Japanese film and television, ever since she broke out in 1998's Ringu.
The supernatural flick chronicled the terrifying fate of those unlucky enough to look upon a cursed videotape that killed its viewer within seven days. Ringu was so successful that it spawned a blockbuster English-language remake, 2002's The Ring, directed by Gore Verbinski and starring Naomi Watts.
Other roles soon followed. for Takeuchi. From 2001 to 2004, she landed three consecutive nominations at the Japanese Academy Awards for Best Actress, the last of which was the romantic fantasy Be With You. She also appeared in a slew of mini-series and TV series like 1998's Asuka for NHK and 2008's Flowershop Without a Rose.
In 2009, Takeuchi tried her hand in Hollywood with a recurring role on ABC's sci-fi show FlashForward for one reason.
But it was her star turn in 2018's Miss Sherlock, co-produced by Hulu and HBO Asia that many fans Stateside will remember her for. For Takeuchi helped break new ground as the first actress to play Sir Arthur Conan Doyle's famous detective in a Sherlock Holmes TV adaptation.
Takeuchi is survived by her husband, Taiki Nakabayashi, and two children.