Just to be clear, the question is if Britain stays out of the War, might Japan join with the Central Powers?
The answer to that is "yes." There were several prominent Japanese statesmen, mostly of the old-guard genro Choshu faction (led by Field Marshal Yamagata Aritomo) who actually felt the treaty with Britain had outlived its usefulness, and that Germany was the new rising power. Indeed, they had entertained ideas of a Russo-German-Japanese alliance for a time immediately prior to the death of the Meiji Emperor -- a negotiation was actually supposed to take place (according to Japan) but the death of the Emperor postponed it, and it was never rescheduled. Whether the Russians or Germans would have agreed to it is another matter entirely...
Respect for Britain only went so far, but it was part of why the Japanese joined. The then-Foreign Minister Kato was a very outspoken Anglophile, and one who wished to demonstrate the independence of the elected government from the elder statesmen and nobility who attempted to control things absent elections -- so joining Britain was quite rational for him, and done over Yamagata, and other's, objections.