After watching it again, I think the white censor lighting was a Cover request after the animation was already made
None of those white blobs actually covered anything explicit, they just blur the outline of her bare ass or cover something else that was already censored naturally, even the one at the beginning already has seaweed covering her crotch, and this one had Okayu's tail as a censor already
>>33440001Kind of wastes the effort the animators put into naturally censoring her bits but oh well