Lupin the Third vs. Detective Conan

Queen Sakura is killed during a hunting trip in Vespania, and her son Gill dies by suicide, overwhelmed by guilt. The throne passes to Princess Mira, who initially rejects the idea of becoming queen. This tragedy triggers a political crisis as factions question Mira's fitness and the future of the kingdom.

Duke Keith, chief of the Commons, appoints Daisuke Jigen as Mira's personal guard to protect the princess during the coronation. Lupin III arrives in Vespania, and he and Jigen discuss a plan to obtain the crown for their own clients. The stage is set for a high-stakes royal intrigue.

Arsène Lupin III reaches Vespania and joins the effort to grab the royal crown. He aims to exploit the unrest around Mira's succession for a theft that would benefit the Queens of the Realm. The plan threads through the royal guard and political factions.

A festival is held at the Grand Hotel West City Tama to boost Mira's popularity during the Japan tour. Conan exposes a poisoning attempt against the princess, averting a potential diplomatic disaster. The festival turns from celebration to caution as security tightens.

In the aftermath of the incident, Mira and Ran Mouri swap places, with Ran disguising herself as the princess. The real Mira returns to the party scene and explains the impersonation, triggering further complications for the royal entourage. The swap strains diplomacy and law enforcement across borders.

To avoid a diplomatic incident, Duke Keith compels Ran to continue acting as Mira. Conan, noticing the ruse, boards the next plane toward Vespania and is saved from hypothermia by the Duke. The pursuit deepens the international intrigue surrounding the crown.

Inspector Megure recruits Koichi Zenigata to help capture Lupin, and Kogoro Mouri joins as his assistant. The cross-agency pursuit underscores the film's detective-work tone, while Lupin and his allies maneuver behind the scenes. The chase tightens the circle around the crown's theft.

Fujiko Mine visits Mira and terms herself to lead her around Japan while Lupin uses dowsing rods to locate a valuable mineral beneath Vespania. Lupin seizes a piece of the mineral to aid in his plan to steal the crown. The duo's actions complicate Mira's path to the throne.

Mira returns to Vespania after visiting the site where her family died. She resolves to assume her duties as future queen, bridging personal grief with a renewed sense of obligation. Her decision stabilizes the political situation for the moment.

Lupin infiltrates the vault and discovers that Fujiko has already stolen the crown. He must flee with Goemon as alarms draw police, forcing a rapid withdrawal. The caper underscores Lupin's skill and the shifting balance of power within the palace.

Conan and Lupin uncover that Gerard Musca Vespaland, Sakura's own brother and Prime Minister, murdered the queen and the prince to seize the throne and profit from forbidden ore. Their investigation exposes the political conspiracy and names the true culprit. The revelation paves the way for justice and political reform.

With the conspiracy exposed, Mira ascends as queen, and Lupin returns the crown to her. Ran and Kogoro are celebrated as saviors of the realm, and Zenigata ends the chase with a grudging respect for Lupin. The crisis concludes with a fragile peace and a new era for Vespania.

Conan is escorted by members of the Japanese embassy who are really Lupin's gang to help him return to Japan due to lack of legal ID. Lupin reveals that he knows Conan's true identity as Shinichi Kudo, and they acknowledge this unlikely connection. They part with a promise to meet again under different circumstances.

Conan and Fujiko depart for Japan aboard a borrowed submarine, while Fujiko begins to closely investigate the effects of the APTX-4869 transformation on Conan. The epilogue leaves their relationship open, with hints of future encounters. The film ends with Conan's life advancing into an uncertain but hopeful future.