The Tik Tok app is highly popular with teens.
It's originally from China. But it's not only popular in China and Japan, it is e.g. also here in Germany with teens (it made some headlines here, cause some girls were sexually abused there without them even realizing).
This statistic was included in the article about Kuu on Yahoo:
Pink is female middle school pupils, blue is female high school students.
The Megumi no Hito trend is done by girls, but Kuu always was more popular with females with her strong woman image.
Modelpress and Co. have articles about it now as well and she's trending with that topic.
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Megumi no Hito is now also charting on iTunes and recochoku.
It's currently at #46 on iTunes and #62 on recochoku.
They could use that momentum to make her more popular with the public again, e.g. with singing Megumi no Hito at both shows she's announced for, coupling it with the info about her new album.
Though I suspect Kuu doesn't want to.
Imo it's definitely no coincidence, that Kuu decided to include Megumi no Hito in the setlist of AND Tour, after not performing it for some time on a (tour) concert, and this starting in May.
I suppose some young fans went and saw it there and started it.