The band suspects Taki played favorites in choosing Reina in the auditions. Noticing the band's rising distrust of Taki and Reina, he makes a proposal.
That's how I knew about Taki-sensei.
هكذا عرفتُ بأمر المعلّم تاكي
Deshalb kenne ich Taki-sensei.
Por eso conozco a Taki-sensei.
Por eso conozco al profesor Taki.
C’est la raison pour laquelle 
je connaissais M. Taki.
Per questo ci conosciamo.
Foi assim que fiquei
sabendo do professor Taki.