The protest happened: ~11k gathered peacefully outside Japan's Diet on March 19 night (not "stormed," and not today). They opposed PM Takaichi's alignment with US policy on the Iran conflict, with chants like "Japan’s future is not in Washington."
Asahi Shimbun poll (Mar 14-15): 82% oppose US strikes on Iran. Video matches reports from Reuters/Asahi. Hyperbole aside, the event and numbers check out.