As you might already know, there is a comic version of 「Hitsuji to Hagane no Mori」 that is illustrated by Mizutani Ai. The final of two volumes has been released few days ago. The obi of both volumes are slightly different =)
Image from Mizutani Ai’s Tweet
Vol. 1 (release date: 26 Feb, 2018)
Purchase @ Amazon| CDJapan
Vol. 2 (release date: 25 May, 2018)
Purchase @ Amazon | CDJapan