Both in character
Kuma starts 100 meters away
Fight takes place at Asgard
Kuma can hit even intangible things such as pain, I don't think he'll have a problem pushing away Respira.
With that said, we have no idea how Kuma really fights. In the Marinefod arc he fought Ivankov and it seemed like a standstill with no side having seemed to have damaged the other significantly by the end. Now personally, I don't think Ivankov was that strong or certainly not at admiral level. So I wouldn't rate Kuma at admiral level at this present moment in time.
So as for this battle, I say, fuck knows who'll win. We really don't know enough about Kuma to decide.
Well technically he did push each of them to a exact location in "space". But still i doubt he could push away the respira because in the process of knocking it away his hand would have rusted to nothing.
This is what I said in a thread before, I think it was the Espada vs Shichibukai but i can't remember. Kuma's hand would likely age if he tries to repel respira. As seen when Luffy punches his hand during the Sabody arc, he has to touch something to repel it. And if he touches respira, he gets aged and dies.