Board Thread:General Discussion/@comment-24396332-20141012160151/@comment-4556650-20141013083332

The character Hawk probably didn't existed back then, so therefore it can't really be considered a cameo appearance. Unless, Nakaba had already planned/designed the characters for Nanatsu no Taizai when he was still working on Kongou Banchou. And if you've read the oneshot of Nanatsu, you'll notice that Hawk doesn't appear, suggestive that he was only designed after the oneshot.