WAIT WHY IS SHIN SACRIFICING HIMSELF?? WHY NOT FIGHT?? WHA- I'M CONFUSEDDD

Following his logic, while he spoke while playing chess, only way for them to win is by killing them all for sure at once. So probably a trap to gather them all at one place and then attack

He says so himself, they arent prepared enough to fight back, also the fact that the opposition's number can't be determined is a disadvantage, so the only solution that he thought of is posing as the king to be taken away, while he devise the counter attack .