Hmm... I disagree with you in that you say the power balance between species is off, but I do agree that losing a sucker being your downfall is probably too easy to exploit.The sucker that Snowpeople have to suck on to keep their body temperature balanced, is that required? Like if he refuses to eat it will he die? Or is this a way to make them seem more human?
I mean if it is the first one, then that seems a bit unfair, considering that is like a major, visible, and extremely exploitable weaknesses. (Vampires have water yes, but they are powerful even for Youkai, so I don't think they are included.) The weakness would be fine, but with lycans (who can wreck an entire room and disturb the campus with only a headache and a nap as compensation.) Vampires, (who are supper strong with great reaction time, so strong that they probably could be considered close to Demi-gods) and werewolves (who probably have the same power potential as Lycans) it would be hard enough to compete. Add in this major flaw and suddenly it seems my character's race is obsolete.
I'm not saying we need to nerf Lycans, Werewolves, or Vampires. That isn't at all what I mean, I just think that the other Youkai types may need less obvious or available weaknesses. (A werewolf or Vampire could easily remove the sucker from a snowman, the glasses from a lamia, or a coin from a yasha.)
EDIT: So it's not life-threatening? Then it's just a preference? Problem solved! However, I'll still continue to explain.
Let's put these races into perspective:
Vampire
Super Powerful, but their brute strength is drastically reduced by the Rosary. Having your own Rosary to use against a Vampire would count as a weakness toward them, though it's something you likely wouldn't have, unless you were preparing specifically to fight a Vampire. Water, however, is very, very common, and paralyzing your foe is almost instant-win under the right circumstance.Summary: Powerful, but their weaknesses are common enough to balance out the raw strength. If anything, they might have a slight disadvantage.
Werewolf
Hm... Speed. Their power is speed. I imagine /some/ strength is implied, though. Their ability is only at its most powerful during a full moon, and during the new moon it is entirely nonexistent. I'd worry that speed might be an easily-abused trait, but considering that their only real power is restricted to about half of the time (taking into account the ascending and descending amounts of speed), this relies heavily on situational use and necessity. I assume that during the day (in sunlight, with no moon in sight) their power is, if not gone, diminished to about half of its current potential.Summary: Situationally, it could be a problem, but their power seems to be weakened more often than not (surprising, actually). If anything, they might also be a little too weak.
Neko
Slashing claw attacks. Weakness... Playable items...? So... You defeat them with catnip and toy mice? Um...Summary: I don't even...
Crow Tengu
Power of wind. Weaknesses are chosen by the creator of the character... Huh.Summary: Wind isn't all that powerful of an element, but it could be useful against other elements (by putting out or amplifying fire, negating icy attacks or simply dodging other attacks). A weakness chosen by the player means this can be anywhere from pansy baby to super-mega-god. Seems fair to me.
Mermaid
Power of sucking life out of others by the bite. So... They're immortal if they keep drinking life out of others? No weaknesses listed.Summary: So... Do they have a weakness or what? I really couldn't tell one way or the other. They might be somewhat overpowered. Luckily no one chose it!
Succubus
Deceptive illusionists who seduce Humans, but not other Youkai? Weakness is chosen by player. Long nails for claw-attacks.Summary: Again, when the weakness is varied, the result is variable. Since attraction only works on the Human, it's practically irrelevant to the RP (except, of course, that single Human, who was no threat to begin with). Illusions can be very effective, though I imagine less so on a more intellectual race, like the Lycans and Mages/witches.
Snowperson
Ice-elemental creatures who, like other races, uses claw-type attacks, only this time with the element of cold added in. From the description I can only assume that they are able to create their own cold attacks, like icy breath or blizzard or something. They have suckers that lower their body temperatures. Weather plays as a weakness.Summary: Control of the ice element, albeit snowy attacks or icy claws. Their only weakness is Weather, though I think it'd be safe to assume that fire is a weakness (a deadly one, in fact). Weather, as a weakness, is variable, and can be completely avoided indoors. I believe they might also be slightly below average.
If I may make a suggestion? I believe the temperature of their own body should be a key factor in how much power they have. Therefore, the sucker would be an amplifier for their abilities, as well as a comforting object.
Lamia
15 minutes worth of Mind control, the ability to pin enemies if they've been in Youkai for for 30 minutes or longer. Weakness is sight, they are blinded if glasses are removed.Summary: Hmm... Honestly, this one might be overpowered, depending on the personality of the character (and how they'll act in a fight or flight situation). Things like mind control are very exploitable, to a bunnying/godmodding level. On the other hand, complete blindness is a near-fatal weakness if properly exploited. I imagine there is a resistance to mind control by the intellectual races, however the flower-power sounds like it should be potent on anyone. This race seems overpowered, to me at least.
Another suggestion? After researching a bit about snakes, I've learned some things about them that might be useful in balancing them out. They fear fire, so this may be an exploitable weakness, and an elemental one. The back of a snake's head is a soft spot, hitting it could knock it unconscious. Lastly, they faint when their tails are stepped on. Again, these are only suggestions.
Yasha
A summoner, sending monsters to battle for them. Their summons often fail, bringing about the wrong monster. These summons require a coin, so if the coin is taken, the Yasha is useless.Summary: They have the flexibility of ability, as they can summon a variety of monsters. Their weakness is the mishap of incorrect summons, and they are practically Human if they don't have the coin to summon with. I think this is fair, if not underpowered a bit, considering how terrible it'd be to lose the coin.
Youko
Fire foxes. Weakness is listed as naivety, though I imagine their powers are gone, if not weakened, by water, rain, etc.Summary: Pretty much even on pros and cons. Doesn't get much simpler than fire.
Mage
Magic and spells and whatnot. Intellectual, so resistant to mind-based attacks.Summary: Varied by spells, with seemingly no other weakness than the fact that other Youkai tend to hate them. This seems about even, maybe a bit more powerful, due to a wide array of spells, though it would vary with the character.
Human
Weak and fragile little meatsack with no powers.Summary: Must be made of Paper Mache, or Raditz.
Lycan
Pure-blooded Wolves with Human forms. Abilities of Telekinesis, which are self-damaging to the user dependent on amount of power used. A double-edged sword, if you will. Weak against magic powers, but resistant to mind-attacking abilities.Summary: Pretty much even, seeing as they are pretty much free kills once they over-use their powers. However, they are weak against magic, and don't have the greatest defense. A proper beating will fell a Lycan faster than most other races. The upside to this is that they are often lean and flexible, and are able to dodge some attacks. Consider this the Rogue of the Youkai.
Fairy
Puny, magical creatures who make ridiculous deals, and use mirrors to reveal Youkai forms. (Fortunately no one has done this to Ryuu... Yet...)Summary: Not suitable for battle, more for pissing off Youkai.
FINAL ANALYSIS
I think they're pretty well-balanced altogether, though some of those suggestions might level the playing field more.
I do like the fact that, if you choose to look at it this way, it's pretty much just a type-war, for the most part, as some Youkai are resistant to or weak against the abilities of other races.
I was also gonna make a little chart showing which classes had power over other classes, and weak to others, but seeing as this took me a while, I might hold off on that. (I started this yesterday)