Who Could the Rokkisei Be?

is episode 30 of the Beelzebub anime.

Summary
Furuichi and Oga survey the school from the roof searching for emblems on people's shirts, and Azusa ends up tagging along in their search. Two students from St. Ishiyama are seen hassling two of Aoi's gang, causing Shiroyama to interject, telling them to leave. The two disgruntled students are offered a free punch by Shiroyama as compensation for breaking off their advance on the girls. They roll a large weight onto Shiroyama, hospitalizing him. Kanzaki bursts into the classroom the two boys are in later that day to get vengeance, only to be knocked out by Miki in one blow. Miki the invites the students of Ishiyama High to meet him on the roof after school. Himekawa, Natsume, Furuichi, Oga and Aoi all go to the roof after school, though Furuichi stays in hiding. Another member of the 6 Holy Knights is revealed, Go, from the Amateur Radio Club. The four known members of the 6 Holy Knights are all waiting on the roof when the Ishiyama High students arrive. Natsume fights Go, while Himekawa faces Sakaki, and Oga stands against Alex. Oga attacks Alex, knocking him out in one punch. Miki steps in to challenge him, claiming to know Oga from a long time ago, and to have surpassed him. Oga claims to not recognize him, but takes him seriously, passing Baby Beel onto Aoi in order to fight properly.