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.
Everybody who's never 
done it before says that.
Das sagt jeder, 
der es noch nie selbst probiert hat.
Todo el que nunca lo ha hecho dice lo mismo.
Todo el mundo dice lo mismo.
Tous les gens qui n’ont jamais essayé 
disent la même chose.
Todo mundo que já tocou me diz isso.