"He’s gonna reap what he sowed. And it sure ain’t wheat."

It sounds like a 1970s kung fu extravaganza from Shaw Brothers, and there are some strikingly unusual martial arts on show here, but they won’t have Carter Wong worrying too much, because Eagle vs Shark is, in fact, a quirky independent comedy from New Zealand. The title refers to the costumes the two main characters, Lily and Jarrod, wear at a house party cum video game competition run by the self-confessed "complex" Jarrod. Lily effectively gatecrashes the party by using an invite intended for a vacuous co-worker but she is determined to go out with Jarrod by any means necessary. Jarrod, meanwhile, is honing his gaming skills into physical reality, preparing for a revenge fight against the school bully he blames for ruining his life. Returning to his hometown and his eccentric family he prepares for the ultimate showdown. But will loyal Lily remain at his selfish side?

A more apt title might well have been Geeks in Love as this unconventional comedy romance focuses on two characters whose expectations are at odds with reality. Lily is constantly upbeat in the face of adversity – she loses her job in the Clerks 2 style Meaty Boy Burger Restaurant by ballot, a ballot she later finds out consists only of her name. More worrying is her faith in sci-fi geekboy Jarrod who basically treats her badly because of his self-obsession, despite the fact that they both have moles in identical places – how much synergy is that?

Jarrod’s unwavering self-belief in his many talents provides much of the film’s comedy. "Guess I’m gonna have to keep creating or I’ll die" he says with brash earnestness as Lily admires another of his masterpieces – a collection of poorly moulded candles. All these scenes are shot and acted with such deadpan sincerity that the lines between comedy and despair are, at times, desperately thin. When Jarrod declares "I hate to dump you, I’m busy with the revenge mission" you don’t know whether to laugh at the absurdity of it or cry at his stupidity in casting away the only person who loves him. When we later see him practising his diabolical martial arts kata in the sea the picture is complete – he seems beyond redemption. But ultimately this is what makes the film so amiable; love in the unlikeliest of situations against apparently insurmountable but all too human odds.

Writer/director Taika Waititi’s debut feature (he previously directed a number of award-winning shorts) is high on eccentric characters and memorable one-liners. There are no apologies for this oddball menagerie and the only genuine scorn is levelled at the beautiful "normal" people who barely invade the screen’s space and even then are quickly ignored by the intense but forgiving Lily. Which is just as well – Lily not only has her own brother to worry about but also those surrounding Jarrod; his geeky friends, Jarrod’s wheelchair-bound, his sister and her husband who sell dubious cosmetics and have their own unsuccessful range of designer tracksuits.

Eagle vs Shark goes a long way to please its audience with endearing central performances and lots of laughs. Its eccentric style (which also features animated sequences and some charming pixellation in the main narrative) and kooky script combine to make a warm and uplifting indie romantic comedy with enough darkness and humanity to ensure it never even begins to stray into saccharine fantasy.

Eagle vs Shark opens in the UK on Friday, 17 August. It opens in New Zealand on 30 August.