Bus to Oirase/ Lake Towada

Is JR bus the only bus to access to Oirase?
Does JR Hokkaido Tohoku- South Pass cover the JR bus ticket?
If no, how much is the ticket for return?

Thanks!

Is JR bus the only bus to access to Oirase?

In the regular year, there are also non-JR buses from Shichinohe-Towada Station to Oirase; however, they do not run in 2022.

Does JR Hokkaido Tohoku- South Pass cover the JR bus ticket?

No, it is not covered. But it is covered by the JR East Tohoku Pass and Japan Rail Pass.

If no, how much is the ticket for return?

It depends on where you depart from and where you get off. From Aomori, the one way fare is between 2350 and 2740 yen. From Hachinohe it is between 1990 and 2300 yen:
https://www.jrbustohoku.co.jp/route/detail.php?r=178&rc=11

This is not directly related to your question, but if you plan to stay at Lake Towada at least 1 night you may want to consider an hotel offering shuttle service to or from Hachinohe.

Thanks for the info!
In that case, I may consider the JR rail pass instead. With an additional 5K and one more extra day of coverage.