The mysterious group of five was the St. Omiya Girls High School Railways Club who saw Usagi and others as rivals! And we find out why Nishiki sees Usagi as her enemy.
Oh, so you're a childhood friend 
with that girl from Urawa.
إذاً أنتِ صديقة طفولة لتلك الفتاة من أوراوا
Ach so, du kennst diese Urawa
also schon seid ihr klein wart.
Ah, então você é amiga de
infância daquela garota de Urawa.
А, так ты в детстве дружила
с той девочкой из Уравы.