I also don't think that Tendou bit Kazuomi. The "bite mark" Tendou left looks like it could actually be his blood from when he bit his lip earlier. If you look closely, only the bite mark from Kadota is bleeding. I think what Kazuomi was trying to say before Tendou silenced him was the answer to Kadota's question about whether this was the effect of the contract. Maybe Kadota wasn't able to punch Tendou because Kazuomi was in between them and it could have been taken as if he was trying to hurt Kazuomi. At least that's what I want to hope because I ended up shipping Kadota x Kazuomi. I mean, I don't mind the immoral sandwich either way though.