Chonaikai

Neighborhoods in Japan tend to be organized in voluntary associations called Chonaikai. These organizations deal with issues concerning it's members. They are funded by small fees called Chonaikaihi. After moving into a neighborhood expect a visit from the local association (as seen in Yotsuba& volume 1 when Fuka brings over the papers to Yotsuba's house). The work is done by volunteers with some chores rotating amongst the members. For more complex events like festivals they have meetings and plan things out.

Some things these associations do:
-generally they circulate Kairanban. Kairanban is like a newsletter that has official announcements, local crime, community news, dates of festivals, etc.
-hold evacuation drills in preparation for earthquakes, typhoons, floods, and so on.
-act as a neighborhood watch
-hold festivals
-Cleaning up the town, cooperation with and instruction of separated collection of recyclable garbage, etc.
-Improvement of social welfare for community residents
-Promotion of and aid for children’s clubs and clubs for the elderly, participation in radio broadcast calisthenics, etc.

Chonaikai shows up a few times in the Ranma manga like in the above picture where a member is asking Soun and Genma to help catch a panty thief (Happosai).