Two aspiring adventurers, Sinbad (voiced by Hideo Kinoshita) and kid sidekick Ali (Tetsuko Kuroyanagi), rescue an old man washed up on the seashore. Before the old man dies he gratefully bestows them with a map to 'treasure island.' So Sinbad and Ali set sail, saving a baby whale along the way that then follows their ship, helping them out of numerous scrapes. Eventually they reach a faraway kingdom where a misunderstanding lands them in trouble at the palace of the local Sultan, thanks to his scheming Vizier (Ichiro Nagai). There Sinbad catches the eye of the Sultan's beautiful daughter, Princess Samir (Kyoko Satomi). Reluctant to marry the slimy Vizier, the Princess sneaks aboard Sinbad's ship. With the Vizier and his men hot on their heels, Sinbad and friends face untold perils in pursuit of the fabulous treasure.
The picaresque plot, while simple, proves inventive and involving and undoubtedly thrilled kiddie matinee audiences at the time with plenty of action and daring-do. Sinbad performs so many heroic feats its a wonder the crew ever managed without him. Tezuka's progressive influence is apparent in the outspoken Princess Samir who rejects her traditional subservient role, dons a male disguise (just like the heroine of Ribbon no Kishi a.k.a. Princess Knight (1967)) and joins Sinbad for a life of romance and adventure on the high seas. However when faced with danger she disappointingly reverts to damsel in distress mode. Stilted voice-acting in the English dub goes against an otherwise carefully crafted and sober tone. Largely devoid of juvenile humour, Sinbad sets out to ape old school Hollywood swashbucklers. Young heroes Sinbad and Ali are earnest and forthright and earn the admiration of the more seasoned crew. The film also feature multiple musical numbers including a sexy sequence with a strikingly animated dancing girl. However the tunes themselves, while pleasant, are unmemorable examples of early Sixties J-pop. Once the action hits treasure island events take a turn for the surreal pitting Sinbad against the expected giant bird (or Roc), man-eating plants, a huge Gryphon able to shoot laser beams through its eyes and, weirdest of all, jellyfish ghosts (?).