Jun is doing her best to meet the expectations of the students.  She's very popular with the students, but she's been possessed by a loose soul.  And so, Keima begins his conquest of Jun.  However, she's preoccupied with becoming the ideal teacher, so she only sees Keima as a student.  In order to break free of the teacher-student mold, Keima decides to approach Nikaido, who was Jun's senior in school...
because it involves things 
you don't want to talk about.
porque involucra cosas de 
las que no quieres hablar.
porque está relacionado con cosas de 
las que no quieres hablar.
porque isso envolve coisas
 que você não quer falar.