Mafia 30. Yakuza Clans war.

Indeed, some players don't even bother reading the rules properly. Does anyone think that one of the Mafia factions didn't place an order? Are there those who believe that the "good guys" spared the city? Just out of curiosity.

Then does he have the right not to participate?

I don't know, but the rules don't say anything about that. If he can avoid killing anyone in that case, the Mafia will surely get rid of him.