To enter, follow the official Banyaro twitter account and retweet this particular tweet.
To celebrate its 30th anniversary, KenPro agency is giving away autographs from 30 of its seiyuu, including Kiiyan.
Per the instructions on the image, all you need to do is follow the official KenPro account and retweet from it between 1/5/15 ~ 1/23/15 at 18:00 JST. 30 lucky winners will get chosen for the autographs. (You will need a Japanese address for shipping.)