If one group went left, and one group went right, and at least one sister made it to the top from both sides, how did they not see Fuutarou on the trail anywhere, before he just magically surprises them by showing up? I suppose there could've been a restroom on the right path just like the left, and by coincidence maybe the boys were all in there when Yotsuba/Miku went past, but I guess that's just oddly convenient.