I really hope there is a sequel. Even just seeing more stuff by him along the same themes would be good. Reverse ntr is so rare (or male:netorare if you want to call it that).
She (Mizore's a girl and a hot one at that) probably got permission from Comic Shingeki, the publication label part one was in. There was probably some legal things to sort out as far as creating a doujinshi sequel of a licensed work or something, which is why she's re-releasing part 1 as a doujinshi for C108