I've seen it from time to time. I've thrown money at it to make it go away when I'm flush with cash, which as it happens is quite often. And amusingly, the last time I had it come up I simply ignored it, and kept particular vigilance to the seas on each side (because with Nanban you can crush anything stupid enough to take you on) and intercepted a full stack floating my way and sank it. Events like that amuse me no end.

Cracked me up that a clan with no physical connection to where I was at the time province wise on the map was peeved enough to come at me, but then again, not all that surprised because even with the tech tree research that improves clan attitude towards you, no one on the map much likes Christians, and even less so when I'm inciting half the island and recreating the map in the image of one huge rebel army ripe for abuse.