It's a slice of life comedy about Jesus and Buddha flatsharing in Tokyo. It has no plot, but that doesn't matter. It's lovely. It floats along on its charm.
I was cautious because it's by Hikaru Nakamura, who wrote Arakawa under the Bridge. Fortunately I preferred this. Nothing really happens in either show, but somehow it's impossible not to enjoy hanging out with Jesus and Buddha. They're adorable. They're so clueless about the modern world and so enthralled by simple things like amusement parks and bargains at the supermarket. Jesus is a lovable idiot who believes in Santa and can start conversations with scary yakuza because it hasn't occurred to him that a Buddha tattoo doesn't necessarily imply deep religious faith. He also has a blog. Meanwhile Buddha is more practical, guards the purse strings (largely from Jesus) and is capable of sulking in the toilet for three hours.
(No, really. Jesus believes in Santa. At one point Buddha's trying to organise a surprise birthday party for Jesus, but it's hard to hide the fact that Christmas is coming. Jesus though doesn't realise. He's vaguely aware of his birthday, but he hasn't realised that the human festival of Christmas has anything to do with this and thinks it's celebrating Santa's invention of reindeer-powered flight.)
Theoretically our heroes are trying to hide their divinity from the humans, but they're not really too fussed. They'll tell each other if they've started glowing (Buddha) or bleeding from his stigmata (Jesus). They'd panic a bit if all the hosts of heaven dropped by at their apartment. However they're likely to forget and be themselves when talking to passers-by in the street. Say something religious and they might reply with "he's off-duty".
There are three small boys who like flicking rubber bands at Buddha's forehead. That's the nearest this film gets to having a storyline. "The target will definitely be at the festival."
This manga is award-winning (a Tezuka Osamu Cultural Prize), has often been among of Japan's twenty best-selling manga and even got displayed at the British Museum in 2011. However I don't think you can buy it in America, because the Japanese publisher has refused to licence it there, for fear of offence. No one worried about Buddhists, obviously. Japan's a Buddhist country. (Ish. Theoretically.) They knew a Buddhist would see the funny side. However Christianity and Islam have a reputation for being a bit more touchy (e.g. jihad, fatwa, crusades, etc.), although personally I think the Japanese publishers were being over-cautious. I was once asked if I'd be offended at this manga. Ahahahaha, no. Apart from anything else, it's fairly accurate theologically and is absolutely uninterested in parody or making points. It's just laid-back character-based comedy.
(The other two countries that will never see this manga, more surprisingly, are India and the Philippines. The latter I get. They're the only Asian Christian nation. India though actually has more Christians than Buddhists, despite being the latter's birthplace, and in both cases we're talking about a tiny fraction of the population. India's religious fundamentalists tend to be Hindus. Ah well. If Hikaru Nakamura thinks it would be unwise to sell her manga there, I'm sure she's probably right.)
I also own the DVD of a ten-minute OVA of this, as it happens. It came free with a very expensive release of the manga. It was a bit amusing, but almost impenetrable to a newbie. It doesn't have English subtitles and so I was missing Japanese puns and cultural references. (The film has quite a few of these too.)
I'm not wild about the English title, incidentally, although I can't see a better translation. "Onii-san" means "big brother", but it can also be used as an all-purpose pronoun/greeting for any man of an appropriate age. You can use "sister", "uncle", "grandad", etc. similarly. It's warm. To me, it has a friendly air (although it does also suggest respect as well as endearment). Using it for Jesus and Buddha suggests a familiarity that's in itself amusing and hence a perfect name for the manga, whereas to me "Saint Young Men" feels a bit stiff.
The film's nice. It's also quite an original Christmas anime story, for the relatively short time that it's looking at Christmas. (The film then continues naturally enough with Japanese New Year celebrations, giving the film's third act a happy holiday spirit... but alas that wouldn't mean as much to an audience that's unfamiliar with Japanese New Year.) It's not Monty Python's Life of Brian. It's not deep and it's deliberately not giving itself teeth. This isn't something to be analysed or dissected, but instead simply enjoyed.