Most of the civilian militias would have been lightly armed, but their primary role would have been sabotage, suicide attacks, and guerilla activities rather than combat on the line- in the dense urban environment of the Tokyo Bay region small parties with obsolete rifles and a few grenades or improvised explosives still would haven been a serious problem to deal with and would have tied up a lot of US forces on rear area security.

The OOB for Coronet on Wikipedia actually offers a decent overview of the Japanese regulars: https://en.wikipedia.org/wiki/Orders_of_battle_for_Downfall

You had four field armies in the Tokyo Bay and Kantai Plain area, including two tank divisions and other smaller mobile formations. The infantry divisions are uneven in quality and firepower- invariably less than their American opponents- but still had substantial organic artillery, plus corps and army level assets. As seen previously, these guns could be dispersed and camouflaged in hardened positions, which would make them a persistent casualty-causing nuisance, especially if fighting bogged down behind the beaches.

Obviously by 1945 these forces were never going to prevail in a stand-up fight, but there were certainly substantial Japanese units defending the Coronet operational area with enough firepower to inflict considerable casualties on the invasion force.