Ruka is hellbent on knowing the full story behind Kazuya and Chizuru's relationship, and once she does she decides to take action.
There's no difference between 
zero-timing and two-timing!
!لا فرق بين أن تكون عازباً أو تملك حبيبتين
Wen juckt’s schon, ob zweigleisig
oder nullgleisig!
¡Dos novias o ninguna es lo mismo!
¡Dos novias o ninguna es lo mismo!
Nessuna ragazza o due ragazze, non cambia niente!
Ter duas e ter nenhuma é ruim igual!
Две девушки или ни одной — всё враньё!