開幕【かいまく】
raising the curtain, opening (of an event), start, beginning
幕府【ばくふ】
shogunate, bakufu, shogun's headquarters, Imperial Guards office, residence of the Imperial Guards commander
内幕【うちまく】
lowdown, inside information, hidden circumstances, inside facts, inner workings, undisclosed circumstances, inner curtain (in a military encampment)
序幕【じょまく】
curtain-raiser, prologue