Kokura is a city you can walk. There's enough energy in the streets that you don't need a plan — just head into the covered arcades and follow your instincts. A full day on foot is easy here, with coffee stops along the way.
The main hazard is the arcade system itself. The indoor and outdoor sections connect in ways that make it easy to lose your bearings. Bring a compass if you're navigationally cautious, and don't use a pachinko parlour as a landmark — they all look the same.