When it comes to BESM d20 I have no idea how to gracefully address the elephant in the room, so I think I just have to swallow my writerly pride and do it gracelessly - this thing is just profoundly ill-conceived. At some point, pretty close to the start of the entire project, someone made a serious error in judgement and that error led to the book being written instead of the infinitely more sensible alternative of it not being written.
You see, Big Eyes, Small Mouth d20 was meant to be the "anime rpg." I trust you can see why this might be a bit of a problem.
We in the rpg hobby occasionally throw out extremely broad words like "cinematic" or "narrative" to describe our goals for a particular system, and by the strictest dictionary reading "anime" is technically less abstract, but that hair's breadth of extra specificity is an illusion. You use a word that could be plausibly applied to anything and it naturally transforms to jargon (for example, "narrative" in rpg terms usually means "rolling dice less often than expected"). You use a word that can merely be used for almost anything and it just becomes a fog. "A cinematic rpg" probably just means you're glossing over verisimilitudinous details. "The cinema rpg" could mean anything at all.
Which is exactly what happened with BESM d20. It gives us a diverse list of classes that run the gamut of anime stories - Mecha Pilot, Ninja, Pet Monster Trainer, Magical Girl, Sentai Member, Student, etc and it never quite grapples with the fact that those are all ideas that could be the central premise of a complete stand-alone game.
Now, lest you think me obtuse, I must concede that "universal" systems exist. I've got a few on my shelf and some of them are pretty good. Hell, the d20 SRD that forms the backbone of this very book may be considered one of them. But what those universal systems have that BESM d20 generally lacks is a sense of modularity. You take a good universal system like Chuubo's Marvelous Wish Granting Engine or Fate Core and you find mechanics that are as abstract as the space they're staking out. The rules dictate how you interact with a quest or an aspect or what have you, but the mechanics don't depend on how those things are defined, so you can zero in on a particular genre or feel by choosing what those greebles actually are.
Then you have less good, but still competent universal systems like GURPS or d20 Modern that handle the problem of modularity by the simple expedient of being very long and having a bunch of supernumerary rules. You want to play a specific game, you get the specialized supplement that covers your idea and you ignore the stuff that doesn't apply to you. And to be entirely fair to these games, that approach neatly avoids the main pitfall of more abstract games - that player-defined greebles can feel superficial and arbitrary.
BESM d20 technically falls into this latter design camp, but it's unfortunately half-assed about it. Occasionally, it remembers to remind you that the rules are modular, but it doesn't actually show you how to use any of the modules and it's very inconsistent about providing rules that let you simulate its inspirations. Like, a Pokemon ttrpg would be pretty cool, and you can kind of get there by taking the Pet Monster Trainer Class and focusing on your "Pet Monster" and "Train a Cute Monster" Attributes, but there's not much support for collecting a variety of monsters, levelling them up and evolving them into more sophisticated forms, capturing them in the wild, or even dueling with them in an arena setting (beyond just running them as extra characters, that is). You can do it, sure, but you can't do it well, and worse, you can't really do it in the five distinct ways you'd need to have an entire party of Pet Monster Trainers with their own niche protection.
Part of the problem is just that the book isn't nearly long enough to achieve its ambition - only 140 pages. That leaves it feeling only trivially universal. (By which I mean that species of inherent universality that comes from the fact that almost every ttrpg boils down to "say a thing, roll a die to determine if the next thing a player says sounds more like success or more like failure.")
The other big problem is that you're probably going to want vastly different things from a slice-of-life high school sports story than you would from a galaxy-spanning space opera, and those things are not generally present. A baseball team needs something distinct for each position to do. Space exploration could seriously benefit from a method of generating interesting star systems. The book forgets to even mention that you're going to want to look into finding those things somewhere else. (Though, perhaps blessedly, this oversight also applies to the "naughty tentacles" trope that inexplicably gets brought up in the "Fan Service" section of the GMing chapter).
Overall, I can't say I liked this book very much. It was dry reading, the fonts were hard on my eyes, and it was so concerned with covering as much ground as possible that it frequently neglected to make a persuasive case for why that ground should be covered at all.
Ukss Contribution: There were things I liked about it, though. It had a certain turn-of-the-century Japanophilia that was occasionally cringy and occasionally problematic (for example, thinking "anime" is a distinct enough phenomenon to base an rpg around), but which never struck me as insincere. So there's no shortage of Cool Things From Anime to choose for this entry.
My favorite example is from the Train a Cute Monster power description: "The character has carefully studied cute monsters in battle."
While I'm reasonably sure that "cute monsters" is being used here as a term of art, I really like the idea of a naturalist who has abandoned all pretenses of objectivity. "Yeah, I study cute monsters, that's why I got into this business in the first place."
(Although, I suspect this is not as distinct a piece of characterization as I might imagine. Sooner or later, most scientists probably come to think of whatever animal they happen to be studying as "cute").
