Apparently, it was a huge secret, until a fan noticed Takahashi Minami’s name in the ending credits. Takamina later confirmed it on her 755 account, and provided some behind-the-scenes photos and other interesting details.

According to Yahoo News, there was a period last year where Takamina dyed her hair black (around June, 2014). Many fans thought of it nothing more than an image change, but apparently it was because she was being filmed for her part on Attack On Titan. The picture in question:

Here are some screenshots of her appearance in the film:

And lastly, Takamina shares some behind the scenes photos courtesy of her 755 account: