Sebastian would be in the Skirmishers' club for sure, and he'd probably drag Nera along to fulfill his obsessive need to beat her. He'd also likely head an Explorers' Club for the express purpose of pulling pranks on everyone who joins, but officially would be for something like exploring all the nooks and crannies of the academy and everything beyond.

Nera would probably also be a part of the Cute and Fluffy club because it's the club where she could probably sleep most comfortably during activities