The latest update in Shindo Life introduced a powerful rework for Tyn Tailed Spirit Gen. 1 and 2. If you want to get the Tyn Tailed mode Gen. 2 which has a 1/25 rarity (meanwhile the 2nd mode Dragon version has a 1/40 rarity), you will have to head to Vinland. You will have to accept the Generation 2 Tyn Tailed Spirit boss mission and then look for the boss scroll location, just outside the Vinland village.
The video below showcases the exact location of the boss scroll. To coordinate yourself you should get on top of the tallest building in Vinland and fly to the scroll location from there. The boss itself has only 10,000 HP so it will be very easy to take down.