The only reason why I wouldn't think Zariya copied is because they have a few manga with the same theme already. But I agree, they are quite similar!
Now that you mentioned it, it kinda does doesn't it? But I think story better than the other one for reasons. (=・ω・=)
omg I love Ai no Kusabi so much <3 especially the older version that covers the entire story (until the end unlike the 2012 version)
Although I hate the sad ending, it was still romantic in a way...
now my tiny kokoro hurts, gotta go find a suit super happy yaoi to fix my mood
btw, I agree with the first comment that many other mangakas have used the theme but it could be that the author of the original novel ai no kusabi was the first one to come up with this agressive/possessive/bdsm-ish yaoi love
lol not saying Zariya copied, but after reading/watching Ai no Kusabi I can't help but comment on the similarities. The pet auction and the pet cockring ish thing really is similar. XD We needed a more light-hearted version of Ai no Kusabi anyways!