The weather in Tokyo at the end of September is warm and comfortable. You might feel a touch of autumn, and a light jacket may be appropriate in the evening. The average air temperature is about 24｡C (78｡F) in the daytime and about 18｡C (65｡F) at night, and the average humidity is about 70% RH during this period.
Current weather in Tokyo/Kanto
http://www.jma.go.jp/jma/indexe.html
