If you're from Sinnoh:

You are about to challenge the gym leader of Sunyshore city, Volkner.

But, on the way, someone bumps into you, causing you both to fall over.

If you're not from Sinnoh:

You took a trip to the Sinnoh region, and decided to visit one of the nicest cities there, Sunyshore city.

You then ask someone for directions.