It's a horror-themed children's anime that wasn't particularly successful at the time. It had been slated for 52 episodes, but it got cut off halfway through. Apart from anything else, it wasn't selling enough merchandise.
Since then, though, it's had four remake series (two in live-action), plus films. What's more, Tomoko loves it. She watched it as a child, in repeats. Watching the original series today... well, it's not always very good. The animation and artwork are very 1960s, while the scripts are capable of focusing so hard on horror that they forget about character-driven storytelling.
I respect it, though. It's memorable. Bem, Bela and Belo are so weird and distinctive that I can see why they've kept coming back ever since. It's also startlingly dark for a children's show, with death, torture and gruesome killings. The tone's sombre and most episodes end with our heroes abandoning their new friends (if any) and departing to continue their lonely vigilante lives.
They're yokai. This isn't that unusual in anime, but what's different here is how ugly they are. They're repellent, not cool. What's more, they know this and want to be human. They spend their days wandering the human world and vanquishing things scarier than themselves.
BELO = in human-ish form, he's a three-fingered, elf-eared goblin. As a yokai, he's like a squashed lizard with its brains outside its skull. He's the smallest and weakest of the three, being childlike in both mind and body, but he's also the only one with social skills. The cheerful, optimistic Bela can befriend anyone, especially other children.
BELA = she's a snake demon. As a woman, she's even creepier. Imagine a muscular, bad-tempered Bride of Dracula, complete with fangs and too much make-up. (She never drinks anyone's blood, but you wouldn't be surprised if she did.) Her weapon of choice is a whip. She's both ugly and sexy, although it's unclear how much of that's deliberate in this art style.
She's awesome. You'd be terrified if you met her.
BEM = gets the least screen time. His monster form's a bigger version of Belo's, but he's usually a big black man in a sharp suit. His eyes have no pupils. Bem doesn't show much personality, being the calm leader and fighter of last resort. If anything's too tough for even Bela to handle, it's time for Bem.
The first five episodes are formulaic. Belo befriends a child and saves him/her from baddies. This makes the show feel very child-orientated, despite the ghost skeleton train to hell (ep.1), mother who tried to have her child assassinated (ep.2), etc. After that, though, things get less predictable. Some of the more notable episodes include:
Ep.6 = devil-worshippers, human sacrifice, the Sabbath and Satan. Yes, with the goat's head and everything. He has a big cauldron full of blood and he wants his disciples' livers. There's also a room of skeletons where the skulls jump on you and bite you. Bem stabs a woman in the back, although it doesn't stop her.
Ep.7 = Belo meets an orphan whose kind old grandad has sold his soul to a demon that wants to kill all humans. They all live together on the demon's ghost ship. The child's mother is actually still alive, but the details of this are one of the more horrible features of the episode. This episode has a child cheerfully cheerfully saying "the assassins have come aboard", after which there's an undead vengeance massacre. This is a WHAT THE HELL?? episode even for this show, with ever-spiralling darkness and no escape for the nice old gentleman who sold his soul. "Grandad will follow later, okay?"
Ep.8 = Belo frees a prisoner from jail because he trusts him. The man says he's innocent and wants to see his son, but he'll be in here for thirty years. Belo is gullible.
He also frees another one who'd threatened to raise the alarm.
Ep.11 = a particularly strong (i.e. freaky) episode. A woman pulls off her face and finds that her other self in the mirror has a much worse personality.
...but then the show started drifting. It starts focusing on horror at the expense of characters. Ep.20, for instance, has a killer car demon instead of a plot. It's like The Omen, which is similarly bitty. Similarly, ep.21 has a Nazi chain gang where women are getting whipped, hanged as an example to the others, falling off cliffs, hanged again and scalped to make wigs. It's shocking. However we're ten minutes into the episode before we have characters driving the story. (That's still a memorable episode, though, and the start of the show's late recovery. It's wrapping a little girl's birthday party with some of the show's most harrowing content.)
The last few episodes do new things, though.
Ep.22 is another of the show's most shocking episodes, with a mother summoning her loved ones to join her in the land of the dead. She doesn't want to do it, but an evil old hag insists. Anyway, Bem goes through the gate to stop the hag. He dies. They bring him back, but that was still startling. (Mind you, I think the episode needed to find a more extreme visual to convince us that he'd destroyed the hag. By definition, she's unkillable.)
Ep.24 puts our heroes on opposite sides. Gullible, bubbly Belo trusts someone instantly, as is his wont, but Bem and Bela end up assisting Belo's new friend's enemies. Belo ends up getting Bela stabbed in the chest. That was an interesting change on the show's formula.
Ep.25 does something similar, although to a lesser degree. Again, Belo trusts someone and helps them do something inadvisable. Mind you, he also tries to demonstrate that he's not suspicious by doing a handstand and turning his head through 360 degrees. (Bizarrely, this works. Small children, eh?)
Finally, ep.26 has a youkai that eats Belo's head (briefly), a pit of moaning bodies without souls and Belo splitting into two bodies. Bela and Bem realise that they could achieve their goal of becoming human by taking over someone's body. (Bela's all for it. Bem has to point out that this would kill the body's real owner.) For that and other reasons, they'll remain monsters. The episode and hence the series ends with our heroes letting themselves get burned to death, although we don't see the bodies and the narrator tells us that they're probably still alive somewhere.
If I had to keep one episode of this series, I'd choose ep.26 for the character journey.
You'll have noticed that this isn't an upbeat series. It has dark, bittersweet endings. (Our heroes can be relied on to defeat baddies, but they themselves won't be finding happiness any time soon.) The theme songs don't fit, though. Those downer episode endings are always followed by the bouncy, chirpy "Bero wa Tomodachi". As for the show's opener, it's magnificent and you couldn't do anything like it these days. It's a jazzy male voice choir and the most 1950s thing you've ever heard. (Yes, the show aired in 1968.)
Is this a good series? Not really. The storytelling's dated and it too often gets lost in its own horror. (I don't count the animation as a negative, because it is what it is. That's the era for you. Today, though, it's crude.) However, the show's most extreme episodes are hair-raising and its three heroes are super-memorable. I'll definitely be watching the other series.