Thanks for the translation!
As far as her falling, one's sense of balance is controlled by the cilia and the fluid that's in the inner ear, the cilias are basically the receptors that tell your brain your orientation (as thus spinning around will make the fluid spin and consequently, your cilia will not be happy).
(For a less elementary explanation, go ahead and read this if you're bored:
http://users.rcn.com/jkimball.ma.ult...H/Hearing.html)
Anyways, ear infections usually severely impair one's equilibrium by increasing the pressure in these fluid cavities, often by an increase in the actual fluid in there. This will create dizziness as such the receptors can't function properly with the fluid in abnormal conditions and jointly also often causes tinnitus (aka, ringing and such similar sounds in the ear), I'm pretty sure this is what was happening to Ayu.
With her balance out of whack, one can assume that with her disorientation she took a wrong step/turn/lean/angle and fell down the hole leading to happy fun-time. And now you know the rest of the story...... *theme music*