Just looking on youtube, you can find binaural beats for pretty much anything: inflammation cure, pain relief, changing your eye colour, finding love and becoming rich. All the ones I’ve looked at feature comments from people claiming they’ve helped them.
They can’t possibly do all of the above and I don’t think there a studies proving anything but a placebo effect.
And, without truly believing in them, they never had any effect on me. I’ve tried them in my youth.
Honestly, the anime isn’t even good. Like, I’m still reading the manga, but I had to stop watching the anime something like 10 years ago.
I’ve heard it has gotten better since then, but watching the whole thing still includes years worth of episodes so thinly streched you could probably watch every third one without missing anything. And that’s on top of arcs so long, they are even a slog to read through (Dressrosa and Wano).