Inside a feudal Japanese castle ringed by a warlord’s army, a series of impossible killings begins to turn a besieged court against itself — and the cornered lord, unable to find the culprit, seeks counsel from the one man cunning enough to unmask the murderer: a brilliant strategist he has chained in his own dungeon. Such is the set-up for The Samurai and the Prisoner , the latest feature from director Kiyoshi Kurosawa . Four and a half decades and some 30 films into his career, it is the acclaimed Japanese genre master’s first samurai movie. Janus Films snapped up U.S. rights to the film after its world premiere at the Cannes Film Festival in May and will release it in theaters on July 31. The company dropped the samurai saga’s first trailer on Thursday (see it below).…