Tsubaki Line (椿ライン, Tsubaki Rain) is the home course of Sidewinder. It is located in Yugawara, Kanagawa, near the Toyo Tires Turnpike. The uphill battle (between Go Hojo and Keisuke Takahashi) and the downhill battle (between Takumi Fujiwara and Shinji Inui) happened here.
The top of the pass houses the Toyo Tires View Lounge, which connects Tsubaki Line and the Toyo Tires Turnpike. It is also where Project D mechanics gather and tune the cars before the final battle ensues.