In station after station on this line, if you take the East exit you’ll soon pass love hotels, dusty parks and rundown traditional shopping streets, whereas if you took the West exit and continued walking inland (and probably uphill) you’d soon find huge houses and luxury flats. It’s partly to do with that walking inland and uphill, because the other side of the tracks is low-lying mainly reclaimed land. There are and were the practical problems with flooding, mosquitoes, pollution from the factories on the bay and potentially tsunamis down there. Possibly at least as important, however, is the status of many of the places inland, especially those on hills and slopes. This is often based on a history long before they were swallowed up by Tokyo, and often one associated with the country estates of the aristocracy.
I don’t know other areas so well, but similar reasons usually explain why there is so often literally a wrong side of the tracks in Japan.