Both could be good! Atsumu's going to split off at some point to personally handle Set to keep one of the gods out of the picture for a bit (you know how you send the normal high school jock to go deal with the literal god in your elaborate assassination plot?), so he'll be around mostly for the beginning of that OR if she wants, I think Set's probably going to parting stab Atsumu, and Gavial can find him after he runs off and leaves a blood trail behind.

Actually after the attack could be good too. I already promised Miru that Gen could literally carry Atsumu out of the rubble, since they both live in Yima's manor, and Atsumu is going to get his leg all messed up from falling building bits.

Either way I can offer Gavial a chance to do medic stuff if you'd like!