Where is Carl?

Everyday, I have a 45 minute walk from my weekly mansion (somewhat seedy hotel, definitely not a real mansion) in Akasaka to TUJ in Azabu Juban. I take the same route everyday and I walk there and back at least once. Every single day, there is a homeless man sitting by a sidewalk I use on my commute. Every time I walk past that spot he is there. Usually he is sleeping but I have seen him listening to a walkman, reading the paper with his glasses, eating and peeing. Sometimes he gestures towards me and makes weird, incomprehensible noises, but most of the time he's doing his own thing. A friend of mine who lives in my building named him Carl, and the name just kind of stuck. Everyone who lives in our dorm knows who Carl is and we often refer to him in passing conversation. In the past three months, Carl has ALWAYS been there. Never once, have I not seen him.
Until last week, that is. One day, I was walking to school and Carl was gone. Not only was he not at his usual spot, none of his stuff was there either. Carl always had a massive amount of junk collected around him. This time, there were remnants of it left: a broken umbrella, an empty lighter, but the vast majority of his stuff was gone. When I say the empty area, I immediately got a dreadful feeling. What could have happened to Carl?
When I walked back home later that day, there was new green grass planted over the empty, dirt patch where Carl used to sit. A week later, there is a bright green parking lot in place of the once empty area of land that bordered Carl's home. I have not seen Carl since.
This experience really got me thinking. What is Tokyo's policy toward homeless people? I have seen very few since I've been here, especially considering Tokyo's size. The ones I have seen, at least the ones by themselves, all look like they might be crazy. I see homeless people en masse in parks sometimes, and in boxes in train stations at night. How is it that they allow them in train stations, if they don't allow anyone else to stay inside and wait for first train? What happens to the mentally ill in Tokyo? I learned in a class once that Japan has one of the highest ratios of people in mental hospitals in the world. But where are all of these hospitals?
These are the hidden parts of a city. These communities and neighborhoods are much more difficult to explore. But I am beginning to get curious, and perhaps my next Neighborhood Narratives project will deal with these issues. At the very least, I hope that Carl is OK. I hope that he is happy and has found a new home. And I hope that in his new home he does not get usurped for a parking lot anytime soon.