This particular artist really likes Mokou x Tojiko
and has drawn a lot of stuff for them. Or at least he used to like it; he hasn't drawn the ship in a while.
Other doujins that have Mokou and Tojiko interacting are Left Out by Koge Masaki and みことじ竹日和 by Itomugi-kun, both of which reference their families' historical grudge (albeit in different ways).