I believe this is a trace/edit of Matsuri's face at the end of chapter 9, when he was covering his mouth with his pinwheel.

I think I saw the source on this, but can't remember or find it. It was probably on Twitter, but the post may have been taken down or made private.

MD5 mismatch of http://pbs.twimg.com/media/Ew_f_yyVkAIqWwh.jpg:orig