The 19-year-old leapt 99.5m on her second jump on the Lahti hill to win with a total of 251.3 pts ahead of Slovenia's Maja Vtic (238.7pts) and Japan's Yuki Ito (232.2).
It means Takanashi now has an insurmountable lead of 431 points ahead of her nearest rival, Austria's Daniela Iraschko-Stolz, with only four events left of the season which would bring a maximum total of 400pts.
Takanashi, whose worst result all season was fourth in Ljubno, Slovenia, earlier this month, can still beat her record of 15 wins in a single season, which she set in 2013-14.
Results
1. Sara Takanashi (JPN) 251.3 pts (96.5 + 99.5 m), 2. Maja VTIC (SLO) 238.7 (94.0 + 96.0 m), 3. Yuki Ito (JPN) 232.2 (93.5 + 92.0 m), 4. Daniela Iraschko-Stolz (AUT) 231.6 (93.0 + 91.5 m)
Overall World Cup standings (after 15 of 19 events)
1. Sara Takanashi (JPN) 1410 pts, 2. Daniela Iraschko-Stolz (AUT) 979 3. Maja VTIC (SLO) 798