From
Playing The Game in the Welcome to Yokai Academy subforum:
Moyreau says:
When you want to take an action, roll two dice and take the highest one. If they end up the same, add them together. This number represents how well you did. It’s then compared to a Difficulty Number set by the Game Master or to a roll made by someone else. If you beat it, you succeed!
Two dice are your basic pool, but it can increase or decrease depending on Bonuses or Penalties:
* Bonuses: When you have an appropriate Ability for the thing you're trying to do, add a number of dice equal to your level in that Ability, sometimes, more than one Ability are relevant for an action, in this case, you use the bonuses of both or more! Otherwise, situational Bonuses can also work in your favor, these are decided by the GM.
* Penalties: The same way Abilities give you dice, Weaknesses take them away from you, and the situation also can give you a Penalty.
More dice are handled the same way. With doubles, add them together and compare the sum to any other number rolled. If the added dice are highest, use them. If not, use the other highest die. Triples, quadruples, and so on are all added together.
Let's say I roll 6d6 and get... 1, 2, 2, 2, 4, 4. I'd add the 2s together, and add the 4s together, then take the highest sum, which is 8. That is then considered the result of the roll.