You see part of the accomplices face when they kill Agni, they look young (with no moustache) so it's not Tanaka, thankfully. http://www.mangago.me/read-manga/kuroshitsuji/an/kuroshitsuji/127/pg-8/
Plus I think even if it would have been Tanakasan who was ordered to kill Agni he never ever would have killed him in that sadistic way. I mean like on knife in the back isn't bad enough. I mean Agni was so nice, loyal and sweet, it's like kicking a kitten. And that's a thing only Boa Hancock can be forgiven for. So in conclusion I don't think it was Tanakasan and I really hate the older twin and I think so does Tanakasan( or at least he likes the younger one more)
If Elizabeth killed Agni then I want her dead in Chapter 132 (╯°Д °)╯╧╧
I'm so conflicted! So RealCiel looks so nice in the past but then why did he turn out like this?! I also want the person who killed Agni to die but if it was Elizabeth (since we have now ruled out Tanaka) I'm not sure how I would react. I highly doubt it was her. Her with knives? I don't see it. The use of swords (the one she only uses) and knives is totally different.
Yes! I'm banking on the fact the second season of the anime had another master/demon pair (Alois and Claude). A lot of the time when an anime veers from the orginial work, they still use elements that will appear in the original work in the future (that's why they consult the authors). I can already see several similar elements from S2 of the anime in the manga, so I'm hoping real!Ciel has a contract too. I'm mean, apart from the shinigami, Sebastian is OP. He needs a real rival. :D
So I'm thinking... who could be strong enough to kill Agni and someone close to realCiel to be a accomplice? And I read a comment that it could be Elizabeth that killed Agni, but what if it was Tanaka? Since Tanaka is a loyal butler for the lord, maybe against his wishes he was ordered to kill Agni and that's why he looks so serious (sad?) in the latest chapter when he is explaining everything to ourCiel