He was used to numbering the stations in the city. For him, life is dull. He wandered between stations and watched other people's lives.
And he was just looking for the meaning of existence as if nothing had happened. Thinking about him - why live? Because he feels that living is just a meaningless thing.
Until they met each other at Station 10. Only then did they realize that their world only made sense for each other. As a result, they had the illusion of interdependence, and even couldn't extricate themselves...