The world of hell, Pandemonum, is made up of fallen angels. Mullin is excited to work under Beelzebub, a demon which he has always looked up to… But things don’t exactly go as planned.

Mullin falls from the stairs and a gallant male demon comes to his rescue. His name is Azazel. Mullin wants to imitate this male demon, but Azazel turns out different than he expected...

Beelzebub and Mullin run across someone Beelzebub seems to know. His name is Astaroth, and he's surrounded by adoring girls. He calls himself Beelzebub's older brother, and starts going off on how much he loves Beelzebub. However, Astaroth starts to wonder about Mullin, and goes to visit the two while they were working, leaving behind is own work. But then Astaroth's assistant, Sargatanas, comes to get him, and he seems pretty afraid of her.

Mullin meets a new girl, Eurynome, in a meeting, but every time their eyes meet, she gives him a look of complete disgust. Mullin’s worried that Eurynome hates him for some reason, but he finds out the real reason. Later, Mullin wins some movie tickets, and ends up promising to go with Beelzebub, but things don’t quite go as planned.

Mullin visits the Pandemonium Library along with Azazel and runs into the sleepy bookworm, Dantalion, as well as the ancient demon, Moloch, who always tends to talk in a loud voice. Later, Belphegor​ wants to come up with an excuse to talk to Azazel, so she starts making brownies with Beelzebub.

Beelzebub breaks her heels on her way to the office. Adramelech, Pandemonium’s advisor of all things fashion, vows to fix the heels, and we learn just why Beelzebub insists on wearing high heels in the first place. Later, Beelzebub does an interview with a Pandemonium magazine, and we learn a bit more about her likes and dislikes...

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.

Sargatanas loves the characters from Fluffy Whiskers & Friends. The show and a cafe are doing a joint colaboration together, and Sargatanas would love to go. The only problem is that it’s too cute, and she doesn’t think she’d fit in. Later on, Beelzebub and Belphegor make plans to go to the beach, and ask Adrammelech to help them pick out swimsuits.

Mullin jokes that he might put in a transfer request and Beelzebub takes it pretty hard. Mullin gets worried that he might have upset her, so he goes to Astaroth for advice. Meanwhile, Belphegor can't help but run away when she sees Azazel. Belphegor wishes she could tell Azazel how she feels, but just can't work up the courage, and that's when she runs into him in the library...

Astaroth's always slacking off, not doing his work, and messing around with girls. As always, Sargatanas heads off to find him. After wrangling him in, they stop by a park, and Sargatanas suddenly finds herself having to face her feelings towards Astaroth. Later, a cold front descends upon Pandemonium, but Beelzebub can't handle the cold very well. Mullin and Beelzebub try various things to keep her warm, but Mullin comes up with one last idea...

One day at a tea party, Belphegor accidentally drinks alcohol and falls asleep. Azazel finds her, panics, and goes to look for help. But then a sleepy Belphegor pulls him back...