Looking for Yaoi manga

Looking for a manga with a teacher and student relationship. The teacher bought merchandise (maybe a DVD) about an idol group and the seme (Student) used that to blackmail him. And eventually, it turns out the the seme's older brother is part of the idol group that the uke loves so much. If i remember rightly, it was written by Junko-sensei's assistant. However, I can't remember her name :(

Thanks so much in advance.