That video is from a fan meet during 4jib before Kangin left, they were all crying because of his departure to the army. Kangin had said his goodbyes and it was time for him to leave the stage but he wanted to say “We are Super Juni-or!” one last time and the first time they tried it none of them could say it properly without choking up and crying. It was a really heartbreaking moment for everyone :( Kangin really wanted to say it properly so they said it again and they all started crying again.