Haruki hears about Kazusa's moving from her mother, who she hadn't been on good terms with.  He feels betrayed and angrily confronts her.  But his words force open the door to Kazusa's heart, which she had desperately tried to keep closed so that the three of them could stay together.
It's starting to affect the morale 
of the other music students.
Inzwischen wird dadurch die Stimmung der 
anderen Musikschüler mit beeinflusst.
Empieza a afectar la moral de los 
otros estudiantes de música.
Esto empieza a afectar a la motivación 
de los otros estudiantes de Música.
Cela a aussi une mauvaise influence 
sur l’assiduité des autres élèves de musique.
Está começando a desmotivar
os outros alunos de música.