After the battle inside the Ziggurat, Chizuru and Hayate are horrified to find out that their victory would have cost Koyori her life. They agree to help Tazuna and Koyori, even though they're out of the fight now.  They tell the two of them that in order not to be found in the real world, they need to come up with a name to use inside the Ziggurat when they fight.  After a bit of thought, Tazuna and Koyori's new name becomes "Single Gear".
Remember how we called ourselves 
Dagger Shadow and Blade Shadow?
أتذكران كيف عرّفنا عن أنفسنا بـ "ظلّ الخنجر
"وظلّ النصل؟
Wir haben uns doch Dagger Shadow
und Blade Shadow genannt.
Nosotros nos presentamos como Dagger
Shadow y Blade Shadow, ¿recuerdan?
Nosotros nos presentamos como Dagger
Shadow y Blade Shadow, ¿recordáis?
Nous, c’était Dagger Shadow
et Blade Shadow.
Noi ci siamo presentati come
"Dagger Shadow" e "Blade Shadow", no?
Lembra que nos chamamos de 
Dagger Shadow e Blade Shadow?