The older students are off on a school trip leaving Akari and a needy Chinatsu alone.  Nadeshiko watches Himawari and Sakurako fight and remembers them as 
children.
since you two filled out
 that marriage registration.
ya que completaron 
el formulario de matrimonio.
Después de todo, rellenasteis juntas el formulario de registro de matrimonio.
já que vocês duas preencheram
 aquele registro de casamento.