Hirakawa secured his first victory to join Japanese countrymen Kazuki Nakajima (3 wins) and Kamui Kobayashi (1) as winners in the famed race, which was first held in 1923.
Jose Maria Lopez of Argentina followed a couple of minutes behind for Toyota's No. 7 at the Circuit de la Sarthe in northwestern France.
Lopez was joined by Kobayashi and British driver Mike Conway, his teammates when No. 7 won last year to underline how Toyota has broken the stranglehold of Audi and Porsche.
After a calm night, Toyota experienced a rare blip when the No. 8 punctured with Buemi at the wheel at around 7:30 a.m. and 15 minutes later Lopez stalled and needed an electrical reset, costing one lap.
Ryan Briscoe closed out the race as the Glickenhaus 007 car finished in third place, five laps behind the winners.
American Josh Pierson became the youngest driver to participate at 16 years old, 188 days — making him slightly younger than fellow 16-year-old Matt McMurry was in 2014.
Pierson drove 97 laps as he shared duties on the United Autosports USA team driving an Oreca 07 with Oliver Jarvis and Alex Lynn, finishing sixth in the LM P2 category.
- AP