That is clearly more Mizuki than one stage can handle.
Fans who attended the “S.C. NANANET Fan Club Event VII” that was held at the Saitama Super Arena on November 18 – 19, 2017, got two Mizukis for the price of one, because the “Aniki of Anisong”, Ichiro Mizuki, showed up as a surprise guest to perform a duet of the Mazinger Z theme song with Nana Mizuki.