Trying to figure out the metro connections in Tokyo; how to get from Shibuya to Shinsuku

It turned out to be very easy - especially when we walked back. More and more people where facial masks these days. As I heard, there are four reasons for this: more allergies and earlier in the year (due to the global warming), five dust particles that blow over from china, to protect oneself from viruses, or to prohibit that oneself infects other people.