Asian house martin
イワツバメ
1 sighting
Honestly at high speeds, it’s hard to exactly ID them, but this source and this source both note that there are iwa-tsubame at the peak of Mt Meakan. However this source mentions that there are Pacific swifts so it’s a bit hard to say for sure.
A huge flock near the crater of Mt Meakan, maybe snatching insects out of the air. At the time I thought they were swallows.