Like The Girl Who Leapt Through Time before it, Mamoru Hosoda's Summer Wars is a heady mixture of charmingly underplayed life drama and intelligent sci-fi that never quite reaches critical mass but is nonetheless wonderfully entertaining. That's a weird niche to carve out for yourself.

Summer Wars is a little bit like two different movies. One is a sweet-natured romantic comedy/drama about an ordinary guy who must mix with his fake girlfriend's unordinary family, the other a smart sci-fi action film about the same guy waging an often strategic war against a sentient online menace. Both have their charms. The sci-fi action film has the glitz and adrenaline, setting up eye-popping virtual-reality rampages and fluid aerial fisticuffs while piling on the high-stakes pressure as Kenji and his allies make ever more desperate bids to destroy the AI program Love Machine and Love Machine develops a very un-AI-like grudge against them. The romantic comedy has the characters and repartee. In particular it has Sakae, the steely-eyed matriarch of Natsuki's clan, whose ferocity and flashes of grace and wisdom allow her to dominate the film much the way she dominates her family. Her interplay with Kenji is a masterwork of subtle insight and gentle feeling, as important for the growth she instigates in him as the heart and keen intelligence it reveals in her.

The film's true brilliance, however, lies not in its two different faces—neither of which is particularly novel—but in its decision to combine them. It's OZ and Love Machine that upset the film's admittedly generic rom-com premise, taking it in unexpected and ultimately poignant directions. It's the narrative framework and emotional weight provided by Kenji's sojourn with Natsuki's family that keeps the film from becoming Tron: The Animation. And it's when Kenji's real and virtual lives cross paths in earnest, with irrevocable and tragic consequences, that Hosoda's creation crosses the line from entertainment to excellence. The confluence of virtual and physical reality puts teeth on the feel-good silliness and punch into the fight with Love Machine, culminating in a showdown between Kenji's scrappy alliance and Love Machine that is as much about healing an aggrieved family as saving the world.

Which is wonderful. But not as wonderful as it feels it should be. Everything about Summer Wars says that the film should make a masterpiece-sized impression. Hosoda's direction handles interpersonal subtleties and full-on spectacle with equal and impressive skill. Satoko Okudera's script (from Hosoda's story) is crammed well-written characters and well-earned emotions. Akihiko Matsumoto's score does what it needs to and sounds great doing it, and Madhouse's visuals exceed all possible expectations. The studio gives each world its own distinctive look: lived-in architecture, spring-green verdure, and azure skies for the real world; riotous islands of color and activity separated by oceans of blank space for OZ. People in the real world are drawn in classic anime style, with thin physiques and realistic faces that wear their feelings and personalities for all to see. OZ's inhabitants—avatars, really—are hugely varied and generally cutesy, weirdly menacing in their anonymity, and rendered in a style that manages to be flat and three-dimensional at the same time. Regardless of which world, the film is never less than gorgeous, and considerably more when Love Machine morphs into a mountainous demon comprised of 400 million individual avatars.

And yet, for all its excellent qualities, Summer Wars is no masterpiece. And for a very simple reason: Natsuki. She's a complete non-presence. Any scene, any plot development that hinges on her must rely almost entirely on Kenji or the supporting cast for emotional involvement (and charm). That's mostly the fault of Nanami Sakuraba's colorless performance, but Hosoda can't escape blame either. He gives Natsuki very little to do besides look pretty and occasionally provide a maguffin-like motivation for Kenji's growth. There's an unsettling sense that she isn't a person so much as a prize for Kenji to win... and even then it feels like he deserves better. She is allowed a larger role in the second half, but by then it's too late, and Sakuraba's consistent weakness undercuts most of it anyway.

Sakuraba's performance provides Funimation's dub with an opportunity to substantially improve on the original. And there's no denying that Brina Palencia's Natsuki is vastly superior. Palencia gives a spirited performance that matches Natsuki's lively personality as established by her body language far more exactingly than Sakuraba's cutesy but wan rendition. Any scene where she dominates, particularly the highly emotional ones, is clearly superior to its Japanese counterpart. Ditto the scenes revolving around J. Michael Tatum's more professional rendition of Natsuki's wayward uncle (great-uncle?) Wabisuke. There's a trade-off, however. Switching to English also means switching from yakuza-movie stalwart Sumiko Fuji's perfect Sakae to Pam Dougherty's less-perfect version. Michael Sinterniklaas's Kenji also suffers in comparison, particularly in the film's latter stages when his innate courage begins to assert itself. And the English version as a whole dances less nimbly than the Japanese between humor and pathos. Patrick Seitz's script strikes a practiced balance between respect for the original and the need to adjust the dialogue for rhythm and flow. As neither version clearly bests the other in the balance, sticking to your established preferences is probably the best way to go.

Both the DVD and Blu-ray releases include interviews with the actors for Kenji, Natsuki, Kazuma, Wabisuke, Sakae, as well as director Hosoda. The longest—and least interesting—is Hosoda's, clocking in at thirteen minutes and covering a range of mostly technical subjects. The others are equally dry, but are shorter and at least provide actual footage of the recording process. The advantage of the Blu-ray release over the DVD is, of course, its video quality, which is nice when appreciating the backgrounds and carefully animated real-world bodies but absolutely essential when the virtual-reality scenes start trying to drop your jaw down to your belt buckle.

That Summer Wars is one character (and a few conspicuous coincidences and unexterminated clichés) away from achieving its full potential is no reflection on its entertainment value. It's a tremendously fun and fulfilling film, with a large and largely enjoyable supporting cast, a seriously cool old lady, an unexpectedly strong male lead, and a barnburner of a second half. A smidge of unfulfilled promise is ultimately of little importance next to that.