Quoted By:
Tsubasa and Komachi services are being conducted from the local Ouu and Tazawako lines respectively.
IIRC this is the first time since discontinuation of the Toreiyu Tsubasa and first time for E8 sets.
Also note that there are a few Tsubasa services (~4 per day) that are not operated as Yamabiko-Tsubasa pair. These serivces will still operate direct between Tokyo and Yamagata-Shinjou.