He mostly just wants to make sure Uriel doesn't over-stress himself. And that Hatter finds someone else to spend time with. He also thinks Uriel's presence is especially good for Katou since he's someone Katou actually opens up to. But he's also a constant reminder that Setsuna still has a job to do back home and that he can't runaway to Hatori and the others like he sometimes wishes. But Setsuna enjoys camp teasing Uriel a bit because it's nice to see him in his derp side.

Uriel and the undead at camp?