Everyone was at the dining hall, discussing who should become the leader of the group, tho the others were mostly set on you and Byakuya. Byakuya wasn't against the idea of being the leader, but seeing that the others were starting to argue about the matter, he was starting to think that maybe you and him could BOTH be the leaders, or that he could be the leader and that you could be his co-leader. And seeing that your soulmate mark was exactly identical as his comforted him in his decision.