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.
You're so stubborn, yet you 
don't even know anything.
Du bist so hartnäckig, 
obwohl du nichts weißt.
Eres tan terco y no sabes nada.
Eres cabezota y no sabes nada.
Tu es si collant alors 
que tu ne sais rien.
Você é tão teimoso, 
mas não sabe de nada.