I did a bit of experimenting.
My first path I
Blew up the powder stores
Made friends with Queen Onekaza but didn't leave with her.
I went and killed Furrante and got the Ghost Ship from Aldys.
When I went to Ukaizo, I ignored the battle and let the Principi and Rautai fight it out.
The Ghost ship ignored the storm.
On Route the water dragon fought the guardian at sea and said "now we're even". This may be the event that breaks the guardian. I am not sure what this was supposed to do, maybe weaken the guardian?
When I arrived at Ukaizo the guardian talked to me as an invisible object, minions kept appearing and despawning, and i just walked past.
I went back to an earlier save.
I still blew up the power stores.
My ship was strong enough that I sailed to Ukaizo alone.
No ships waited for me. I weathered the storm and avoided crashing into the adra pillar.
The guardian never came and I don't remember any prompts about the dragon. They never fought at sea.
When I got to Ukaizo the guardian spawned normally and the full fight took place. I continued to the end and all was normal.
