The seven demon brothers decided to take a trip to the beach. Mammon was trying to take a picture of Lucifer's broad torso but kept failing miserably.

Lucifer was ignoring Mammon or was just oblivious, he was watching everyone enjoy the beach. Leviathan was swimming, trying to get a pool of fish so he could make them cosplay as Ruri Hana. Satan was sitting on the shore with a towel, watching everyone while reading a book. Asmodeus was swimming gracefully while randomly posing in the water, Beelzebub was eating the barbecue food, and Belphegor was making a sandcastle. [Apologies if it is inaccurate, I haven't watched the beach episode!]