That Man Was a Sensei

is episode 37 of the Beelzebub anime.

Summary
Baby Be'el is having a great time at a railroad crossing and wishes Oga to sing with him. Oga, however, is thinking about the Izuma's words about demon powers. Aoi, who is happens to be behind them, runs into Nene and Yuka, and they once again assume Aoi is going to confess to Oga. At school, Oga has become a celebrity for the "magic trick" after the volleyball match. Furichi drags Oga into creating another illusion a.k.a. making Furichi disappear by sending him flying using his mindless violence. Aoi, not convinced, confronts Izuma; however, she doesn't make any progress. Later, Tōjō talks to Shizuka stating his fight with Izuma isn't over. The two meet on the roof, and Oga joins in. However, before they can begin, Saotome beats them up and brings the unconscious Oga and Toujou to clsss. This causes confusion (as well as having a new teacher). Nene and Ryōko try to fight the new teacher for harassing Aoi. Aoi questions Saotome about Oga, resulting in more embarrassment on her part. She gets frustrated and decides to invistigate. Oga regains consciousness and leans that Tōjō ran off after coming to. Soatome appears on the roof to close the interdimensional hole created by the fight. Aoi returns to the gym and finds there proof that Oga's demon powers were no magic trick. She runs out when the hole is holes (it sent a big blast into the sky). Hilda appears on the roof to fight with Saotome because she believes him to be and agent of Behemoth. She warns him not to harm Beel. Aoi, meanwhile, manages to catch a glimpse of Hilda's demon powers is action.