They don't call Japan "Musashi"
Musashi is a district that travels around, fact is Japan serves as the host for all "countries" because it is the only habitable area in the world.
I'm pretty sure those two will clash, and If I'm not mistaken and that IS Sasaki, then he is moving in to make contact and start a fight.
If you forgot, Oda clan is also around, it's not possible for them to travel from Mikawa to Brittain at the pace they are flying (Musashi is a friggin Battlecruiser class ship, it's size is that of a fairly big town) in mere 2 weeks, moving something this size takes considerable power at all, and the yaren't traveling at high speeds, although it is mentioned that "Musashi" is a fairly fast ship, it can be caught by a few frigates (and was attacked by a few as well).
Back in S1, they travelled through Oda Clan's territory at top speed, you can easily see how fast it was when Oda clan was standing on their frigate and were clearly observable even though their ship wasn't moving.
Like Masazumi explained, Musashi is ready to leave anytime, so Brittain, even if they wanted to pursue them, wouldn't be able to catch them in time because their fleet is too far, and Masazumi said that their next stop would be 2 weeks from now, so it's not like they are fast, they just plan their moves ahead and expect trouble.
I loved how Masazumi declared war, or at least that's what everyone thought she did

Once again, Masazumi is their best politician, and she's an honest one for once
