According to the producer Hamatani Koichi, he was suddenly told by Endo on the day when they did the costume fitting that Amami was interested to appear in this drama. For a while, Hamatani didn't realise that Endo was referring to Amami and even thought that it was a prank on them until the day of the filming. As Amami had never appeared on TV Tokyo before and that theirs was a late-night drama, he thought that it was a miracle that she actually took the initiative to appear in their drama. Apparently, Amami and Endo had become good friends after appearing in the FujiTV Autumn 2016 drama "Chef ~ Mitsuboshi no Kyuushoku" so she made her intention to participate known to Endo who passed on the message to contact Amami's agency.
Amami commented that she had been enjoying the drama since it aired and was very happy to be able to take part and act with the six actors who are her seniors in this industry. Seeing the six of them together was a sight to behold for her as she had worked with all except Taguchi before.
Sources: Oricon / Sponichi