Comedy is big box office in Hollywood now, with such comic odes to male immaturity as “Knocked Up” and “The 40-Year-Old Virgin” grossing north of $100 million. In Japan, on the other hand, making the locals laugh in a movie theater is still the hardest job in the industry — and the returns for comedies accordingly tend to be modest.

It is also the genre that now produces some of the more imaginative and important Japanese films. Surely, you may think, I’m exaggerating? What’s “important” about filming some funnyman’s schtick?

But consider Satoshi Miki, a director of TV comedy and variety shows who began, in 2005, to make feature films. The early ones, starting with the psychiatrist-gone-wild comedy “In the Pool,” were patchy affairs, with great comic bits and pieces but little narrative coherence.

Then, in his fifth film, “Ten Ten” (“Adrift in Tokyo,” 2008) Miki combined sharp observational comedy (including speculation as to how Tokyo’s hundreds of small clock stores manage to stay in business) with a real story about a slacker student (Joe Odagiri) and middle-aged debt collector (Tomokazu Miura) who take a walk together across Tokyo — and find a measure of connection and meaning in a crazy and chaotic world. The ending is genuinely poignant and absolutely unsentimental.

Miki’s followup to this small masterpiece, “Instant Numa” (“Instant Swamp”), is about another journey, but this time one of self discovery. Also, in contrast to the ambling pace of “Ten Ten,” the new film packs in more gags more frantically, beginning with a dazzling opening montage that introduces the heroine and her past at warp speed. Miki’s unique brand of dry, densely detailed comedy is still much in evidence, however, as is his affection for Japan’s odder corners and personalities.

His heroine is Haname Jinchoge (Kumiko Aso), a hard-charging magazine editor who considers herself a super-rational type, unlike her flaky, easy-going mother (Keiko Matsuzaka), who tells Haname, with a straight face, that she suspects a kappa (mythical water sprite) is living in their garden.

Then, in quick succession, Haname loses her job when her magazine goes kaput, the pony-tailed photographer she likes dumps her and repo men come to claim nearly everything she owns. She finds herself scraping out a bare, lonely existence, with a pet rabbit her only company. Then, after mom nearly drowns looking for a kappa in a nearby pond and ends up in a coma, Haname decides to find a certain Noburo Jinchoge, who says in a letter never delivered, but miraculously discovered, that he is her real father.

Haname locates the address in the letter — a tumble-down “antique” (read: “junk”) shop run by a brusque man with an electro-shock hairdo — Noburo (Morio Kazama), who’s nickname is Denkyu (light bulb). She refuses to believe that he is her father, but Gus (Ryo Kase), a punk rocker who is a store regular, immediately sees the family resemblance.

From here on, a conventional plot would lead to a tender father-daughter reconciliation and a budding romance between Haname and Gus, a decent guy despite his no-nonsense persona. But Miki, who also wrote the script, delivers a stranger, more interesting story in which Haname falls victim to what seems to be a cruel scam — and ends up with a pile of mysterious dirt. Then she has a cracked inspiration — make a swamp out of it.

Kumiko Aso has played plenty of oddball characters in a busy career, from the cute-but-eccentric waitress in “Junkisa Isobe” (“Cafe Isobe,” 2008) to the hero’s prim-but-sexually-twisted-fiancee in “Tamio no Shiawase” (“Then Summer Came,” 2008, but her Haname is something special: a woman who takes after her wacky parents but is also her own determined person, as she pursues a vision that the skeptical, if supportive, Gus, considers mad.

Her payoff — which also happens to be the film’s climax — is not predictable, not logical, but it raised the hairs at the back of my neck and made me smile. I wouldn’t blame you, though, if you thought it a tad silly — and neither, I think, would Miki. This least pretentious, and most original, of comic talents isn’t out to convert everyone. But if you’ve already got a kappa hopping around in your brain, “Instant Numa” will be your cup of — something a lot like, but not quite, mud.