Prefecturals are over and the Iwatobi Swim Club members are pleased by the progress they have made.  A local summer festival gives them an opportunity to relax.  When Nagisa finds out that Rin is also at the festival, he orders Rei to follow Rin and make sure that Haruka and Rin do not meet.
That would be the worst case scenario.
Das wäre der schlechtest 
mögliche Ausgang.
Eso sería el peor de los casos...
Eso poniéndonos en 
el peor de los casos.
Au pire, oui.
Nel peggiore dei casi...
Essa seria a pior situação possível.
Будет плохо.