Lakelezz asked me to do this while I was streaming the other day haha talk about last minute!
This is Hanako-san from the Japanese urban legend Toire no Hanako-san.
Basically she is a ghost of a little girl who haunts the 3rd floor bathroom at schools. You knock 3 times on the first stall and ask, "Hanako-san, are you there?" Then move to the next stall and do the same. Then on the 3rd stall, after knocking 3 times and asking, "Hanako-san, are you there?" she will reply, "Yes."
Depending on where you are, she sometimes is innocent, sometimes a killer.
Thanks to Sumwheat for helping me with the hiragana and deciding on which spoopy story to pick!