According to her post below(her official blog in Japanese),
http://ameblo.jp/akari-mituki/entry-11907448146.html
some audition staff said "Anyone will get baseball bat spanking?" and then her friends answered "Why not her?",so that's why she was spanked!
I can NOT find movie about that,but in her blog we can see pics of her bottom punished that way.
see http://ameblo.jp/akari-mituki/image-11907448146-13029697581.html
or http://stat.ameba.jp/user_images/20140809/22/akari-mituki/73/ed/p/o0239033113029697581.png
