Ryutaro Kotaki, 45, president of a Tokyo bookbinding company, took his life by driving his car into the sea off a pier in the city's Minato Ward at about 7 a.m. March 9, police said.
A passerby reported to police that he saw a white sedan fall off Hinode Pier, police said.
The Tokyo Metropolitan Fire Department retrieved the car about an hour later, but Kotaki, found behind the wheel with his seat belt secured, was pronounced dead by drowning.
Kotaki, president of Chiyoda Graphic Co. of Soka, Saitama Prefecture, was identified by his personal effects, police said.
Four wills written by the man and addressed to his next of kin and others were found in a desk drawer of the company's office in Minato Ward, police said.
In a will addressed to the company's accountant, Kotaki said he could no longer run the firm, police said.