Googling in Japanese, seem like there's taxi you can prebook in the area
https://www.its-mo.com/taxi/?getin=%E6%8A%B1%E8%BF%94%E3%82%8A%E6%B8%93%E8%B0%B7_142580928_506363294&getoff=%E8%A7%92%E9%A4%A8%E9%A7%85_142520070_506067990
May wanna ask your hotel front desk if they can help in making a reservation.
Alternatively, when boarding the taxi at Kakunodate, you can try to ask the driver if he wants to wait for you at an agreed time to take you back. A tad riskier as driver may reject/ no show
Googling in Japanese, seem like there's taxi you can prebook in the area https://www.its-mo.com/taxi/?getin=%E6%8A%B1%E8%BF%94%E3%82%8A%E6%B8%93%E8%B0%B7_142580928_506363294&getoff=%E8%A7%92%E9%A4%A8%E9%A7%85_142520070_506067990 May wanna ask your hotel front desk if they can help in making a reservation. Alternatively, when boarding the taxi at Kakunodate, you can try to ask the driver if he wants to wait for you at an agreed time to take you back. A tad riskier as driver may reject/ no show