Which means that in the "normal" version, she wondered off, hurt herself a little. Youki came and brought her back without seeing the mountian, then Yukari came as a witness for the death happened as normal.
In this version, Sakuya bumps into Yuyuko before she hurts herself, resulting in a chase with Yuyuko running into an Oni who shows her the mountian, they all come back together (with Youki falling for Sakuya suddenly) and Sakuya interrupting the death as Yukari would have witnessed it alone.