Conan vs. Kid vs. Yaiba - The Grand Battle for the Treasure Sword!!

Situation
At Teitan Elementary, Mitsuhiko lends Conan his manga collection - a back-breaking 24 volumes - for some light reading. Conan is intimidated by the sheer bulk, but grudgingly accepts.

Several days later, the Detective Boys encounter a mysterious fortuneteller on a side street. The fortuneteller's crystal ball tells Conan that he will soon find himself solving mysteries at a place with a tiger, a vulture, and a giant frog. Shortly afterwards, the fortuneteller vanishes. Conan is disturbed, but says nothing.

Conan returns to the Mouri Detective Agency with the Detective Boys, only to find the agency's latest clients: Sayaka and Shizuka Mine. Sayaka and Shizuka want Kogoro to protect their dojo's sacred sword, which has been targeted by Kaitou Kid.

Kogoro accepts the request, while Conan notes that he has seen these new clients somewhere before - but cannot remember where.

Over at the Mine household, Inspector Nakamori asks to help protect the sword, but are ejected by Sayaka's grandmother. Despite her further protests, Sayaka and Shizuka invite Kogoro, Ran, and the Detective Boys into the house. The Inspector and his men must make do with watching the house's perimeter. The Mouri family and the Detective Boys are quickly acquainted with the rest of the Mine family, including the energetic, sword-happy Yaiba.

After night falls, the Detective Boys (sans Conan) explore the Mines' front yard, and are terrified by Yaiba's friends Kagetora, Shonosuke, and Gerozaimon. The Mouri family and Inspector Nakamori both jump at the noise, but lose interest when they find it a false alarm. Conan becomes even more disturbed as he realizes that the crystal ball's prophecy has come true.

While Kogoro begins drinking with Yaiba's father Kenjuro, Conan tries to learn the sacred sword's location from Sayaka's grandmother, but is rebuffed. Upon seeing a bottle of baijiu, Conan feigns a cold and asks if he can drink some, hoping to turn back into Shinichi. The old woman misunderstands, however, and gives Conan a glass of homemade cold medicine. Before Conan can ask for "seconds", Ran intervenes and drags him away.

As eight o' clock approaches, Kaitou Kid hang-glides toward the Mine household, but collides with Shonosuke in mid-air and falls into the Mines' koi pond. Kid quickly recovers and resumes his plan to steal the sacred sword, seducing each of the household's three women as they try to stop him.

The rest of the household is alerted to Kid's presence, but only Conan is close enough to give chase. Conan realizes that his legs are too short to catch up to Kid, and takes another drink of the cold medicine, hoping it will re-age him into Shinichi. To his horror, the medicine transforms him into Kogoro; he then stumbles into the real Kogoro, who concludes that he is Kid in disguise, causing Inspector Nakamori and his men to give chase.

Meanwhile, Kid enters the Mine Dojo, and finds the sacred sword being protected by Yaiba. After a quick duel and some trickery, Kid makes off with the sword and escapes on his hang glider. Yaiba refuses to give up, however, and gives chase on a kite. As Kid and Yaiba fight each other in midair, they are spotted by Onimaru, who blasts both of them out of the sky with a cannon.

Conan, hoping to shake off his pursuers, takes another drink of the medicine and turns into Heiji. This does nothing to dissuade Inspector Nakamori and his men, forcing the transfigured Conan to hide in another part of the house. Confused and desperate, Conan tries to piece together a logical explanation, until he comes to an undeniable conclusion.

Resolution
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Conan, now looking like Shinichi, recovers the sacred sword and lays out his deduction.
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Evidence

 * Ayumi is wearing a ribbon instead of her usual headscarf.
 * Genta's ten-yen bald spot is on the opposite side of his head.
 * Mitsuhiko is missing his freckles.
 * The two stray hairs normally dangling from Kogoro's head have now become three.
 * Ran's bangs are parted differently.

Conclusion
The entire adventure was a dream; Conan had fallen asleep reading the Yaiba manga that Mitsuhiko had loaned him.

Manga to Anime changes

 * This OVA was a greatly expanded version of an "extra" chapter from the third volume of Magic Kaito. The original manga version of the story featured no characters from the Detective Conan cast, as it had been written and published before even the first chapter of Conan. Akako is also absent from the original manga version.
 * In the manga, Kid steals the sacred sword from Yaiba almost immediately; in the anime, he uses his card-gun to fence with Yaiba for a bit before taking the sword.
 * In the manga, Yaiba's drunken father interrupts Yaiba and Kid's duel and corrects both of their stances before letting the two resume. This is left out of the anime.
 * In the manga, Inspector Nakamori is the one who recovers the sword.
 * The manga includes a short epilogue that takes place the morning after the heist, where both Yaiba and Kaito wake up with numerous bruises and swear off anything having to do with swords. This is left out of the anime.