I was at the seaside village's dewdrop cavern (where you can find water starters). At the first floor 2 tuber kids ask you to join your party.

So i accepted ( i could use them to wonder trade)

Then, at random locations in the game, police npc will start following you to arrest you. They battle you using higher level pokemon (my team's average level was around 35 while the police's pokemon are somewhere around 40).

So far, the police tried to stop me at Route 8, The Library, Surfin' city's PC and at the entrance of Seaside Cavern.