Tendou is an alpha. It says so right in the summary, even. So I'm confused as to why you thought he was beta... at all?
It might be because after Kazoumi got bitten by both of them he was about to say something about Tendou but was cut off.. And I think he was gonna say "Senpai isn't an alpha" to Kazoumi so it doesn't really have any effect Tendou biting him also. This is just a guess so...
I'm assuming that Kazuomi was going to say "Senpai isn't in love with me/a rival for your affections", something like that. Tendou not being an alpha would be an interesting twist though (however, the summary does say that he and Kadota are alphas).
All in all, this manga was obviously written for the sexy-times and not for a plot. Doesn't mean I don't want more of it though...
It sucks that it's 3 chapters. I don't really like the alpha and omega relationship primarily because it wasn't developed enough. ...well the whole story wasn't developed enough. We only got JUST ENOUGH for the story to make sense. As far as tendou loving the kodota ...well it sucked that the kazuomi is stuck in the middle of it. A little further doen the chapter I believe kazuomi is hurt because he knows thst tendou that loves the kadota. When tendou bit kazuomi I don't think he minded because tendou is a beta. Since kodota bit kazuomi I think kodota's bite basically overpowered tendou's bite since he's a beta. I think that tendou bit kazuomi because basically he can use that bite to stay linked to kodota. (I know I keep using the same words but I really hate typing on a tablet lol)