As Miss Beelzebub Likes It. Season 1 Episode 7

The members of Pandemonium are not getting enough exercise, so they decide to build a gym, but when it comes time for the opening ceremony, Beelzebub and the others find themselves staring at a Japanese-style bath instead. Since the facility already exists, they might as well get in… Later on, Beelzebub learns more about Mullin and the pet he keeps at home.