Hamtaro has recently been troubled by a recurring dream in which a beautiful hamster princess pleads for help. The image lingers in his mind even after he wakes. One winter day, Laura mentions that her entire family will be returning to her father’s hometown. When Hamtaro shares this with his friends, Maxwell brings out a Ham-Ham source book—a record of ancient hamster history.
The book describes a legendary “Hamja Kingdom,” the ancestral homeland of hamsters. Following its instructions, the Ham-Hams construct a sand castle and chant the exact spell written in the book, which instantly transports them to the Kingdom. Upon arrival, they find a lively, bustling land of hamsters, ruled by the beloved King Hamja. They also meet the Mini-Hams, familiar from their earlier adventure in Ham-Ham Land, as well as the Mo-Hams, spirits residing in jars. A joyful parade erupts with singing and dancing. But chaos strikes when the wicked magic cat Sabakunya appears, riding a colossal sheep monster named Mee Mee, and begins rampaging through the town.
The Ham-Hams flee underground, where they learn the Kingdom’s dire situation: Sabakunya has kidnapped the King’s daughter, Princess Shera, and intends to force her into marriage on the Kingdom’s Founding Day, aiming to seize control of the country. Hamtaro suddenly realizes that Princess Shera is none other than the princess from his dreams. Determined to save her, he and the Ham-Hams make their way to the castle where Sabakunya resides. Inside, they face one peril after another, and Hamtaro, chased by Sabakunya’s minions, becomes separated from the group.