Kobeni’s Contracted Devil (theory)

So I was rewatching the anime, and in the earlier times that we see kobeni, she’d always be holding a knife. We have seen that she has great speed and mobility and combat skills whenever she fights. Although a short scene, it shows just how talented she is. Another really talented devil hunter is Kishibe. He is probably one of , if not the best, devil hunters that we see. He has a LOT of experience and he is strong, agile, and lethal. He also has a contract with the Knife Devil. When fighting with a knife, he is seen to be very lethal. Maybe not everyone can make contracts with the Knife devil, but Kobeni could potentially be an exception. I think this is a fun theory, that the small timid girl could have a contract with a strong combat Devil and be terrifying in a fight. As to why she calls it a secret, i’m not quite sure. Maybe Kishibe trained her and don’t want many people to know just how strong the contact could be. Or maybe she just doesn’t wanna tell lol. But it could be that her contact is as simple as with the Knife devil, it’d be something not many people would be expecting tho!