大誘拐 (daiyuukai, The Great Kidnapping, 1979) is a crime novel by TENDOU Shin (天藤 真, 1915-83); and as you can probably guess from the cover, it's a comedy. Although kidnapping is such a horrible crime in real life, it is often used for comedy (the O. Henry story, "The Ransom of Red Chief" for instance, or the Bette Midler film Ruthless People). This one fits into a familiar pattern in kidnapping stories: a victim more forceful than the captors effectively becomes the boss of the gang. Rainbow Kids in the post title is the "English title" added to the book (although it doesn't have an English translation), and refers to the name that the gang give themselves (they call each other by the code names Wind, Thunder and Rain, when they remember). There is a 1991 film of the book, directed by OKAMOTO Kihachi (岡本 喜八).
Three young small time crooks leave prison planning to make some real money. The leader Kenji (健次) is thinking of a kidnapping, to the alarm of the others, who remember horrible news stories of child kidnappings gone wrong. No, he assures them, the target is not a child, but an old woman, YANAGAWA Toshiko (柳川とし子, known as Toji, apparently an old fashioned honorific for a woman running the affairs of a wealthy family). She is the head of a Wakayama family that controls a vast extent of forest land. Unknown to the kidnappers, they have picked an ideal time, as she has taken it into her head to go for a walk every day through a different part of the Yanagawa lands, accompanied only by her maid Kimi.
When the kidnappers, after various misadventures, finally succeed in capturing her, it immediately becomes clear who is going to be in control, when she insists on them letting Kimi go. Soon, instead of heading to the hideout they had prepared, they are staying on the farm of one of Toshiko's loyal former servants. Their plans are thrown out much more drastically, when she hears how little (in her opinion) they were planning to ask for ransom. She insists on a huge sum, far greater than any previous ransom; and the gang agree, very unwillingly (how are they even going to carry a sum like that). Soon the case developes into a game of wits between the old lady directing the gang behind the scenes and the wily police chief, who had got his start in life from Toshiko's support when he was a child, and is fiercely devoted to her. As each side challenges the other, the whole of Japan and the world outside are drawn into the spectacle.
This is not a black comedy. There is no violence and no real villains. Most of the characters rise to the challenges presented them. The humour is mostly in the characters (particularly Toshiko, always gentle and courteous, but sure to get her way) and the situation, not so much in actual jokes or comedy set pieces. The tricks that the kidnappers use to outwit the police are reminiscent of the "caper" style of crime file (like Ocean's Eleven), but the book also reminds me a bit of earlier comedy adventures like John Buchan's John Macnab.
The film is very close to the book, in both substance and tone. The main differences are only simplifications and minor omissions. Occasionally a scene is very slightly more slapstick than the book, but this is rare. One minor difference of tone is the music. Okamoto sets a lot of scenes to upbeat pop music; and this sounds a lot more like 1990 than 1979 to me. It's no classic, but I thought it was a very successful adaption, definitely worth seeing if you get the chance.