Shevuot 13: Does Yom Kippur Atone for Violating Yom Kippur?

On Yom Kippur atoning for sin, regardless of a person's regret. With a dive into Rabbi Yehudah vs. Rebbe (Rabbi Yehudah HaNasi), as to the extent of the atonement and what happens with unrepented sins. And which view underlies or agrees with the mishnah? Also, the sacrifices atone - but only with repentance, so isn't that going to be the case with Yom Kippur too? But even if Yom Kippur does atone without teshuvah, what happens if the thing to atone for is the violation of Yom Kippur itself?