It was likely Manabe or someone Manabe related. If it was Yoshihara why the reassessment or whatever?
Yoshihara is/was the lead candidate as per Hochi. Sports Hochi is the only unbiased publication that also reports on volleyball since Saori's peak so they are credible.
JVA released the men's coach first most likely has something to do with sponsorship and also because Osaka Blueton is currently #1 in the SVL ranking so the timing is just right.