Kikkasai follows the style of Mahjong, drawing dice from a bag, rolling, discarding, trying to complete sets. In this game, you only handle 2 + 1 dice, so your target is to create one single set. Many of the rules match Mahjong; draw 1 discard 1, claiming the dice your opponent discards, or the rule of "trend" which gives you extra points (like the Dora rule in Mahjong).
Initially, one die is placed as the "trend". You get extra points for winning a hand by using a same colored die / same pip with the trend die. Then each player grabs 2 dice from the bag and rolls behind their screen. These dice are the players' hands.
Each turn, if you can use the last die discarded by your opponent to complete your set, you declare and win the round. If not, you grab a die from the bag and roll. If the 3 dice (2 in your hand and 1 just rolled) completes your hand, you win the round and score points. If not, you must discard 1 die, either from your hand, or the rolled one. Be careful not to toss out a die your opponent wants. Now the turn switches to your opponent.
The round ends when any player wins, or the bag is out of dice. Put all the dice back in the bag. If any player has 0 points or less, that player loses. Or else, start a new round, switching the starting player.