The boy who Hayate meets is revealed to be Wataru Tachibana, Nagi's fiancé. However, Nagi and Wataru can't stand each other.
Well, there are all kinds of unknown 
worlds sprawled under Tokyo
Bueno, hay todo tipo de mundos 
desconocidos esparcidos debajo de Tokio
Mas o subsolo de Tóquio é um espaço...