During Kaoru's meeting with the Emporer, what is the Go board used for?

The Emporer has called for a meeting with Kaoru and Kaoru has come to the palace as he was requested. The Emporer uses the Go board to make a vague hint at a wager. The Emporer wants Kaoru to marry the Second Princess, but does not wish to ask Kaoru directly. Kaoru accepts the offer.