If you’re in the south, ally uesugi; if you’re in the north, ally hosokawa. Neither is admittedly guaranteed to be the first dominant threat, but they’re your best bet. Daimyo japan is fun because it’s basically just battle Royale. Pick 4 allies, fab some claims and go nuts. Don’t worry about ae, since Ming and Korea aren’t really gonna care, or seppuku, since, you know, this isn’t ck2 or real life or whatever.

Be aware that the ashikage war is only you and your allies against everybody else on the islands. Most people get worried about not declaring that war soon enough, but really you can wait for quite awhile as long as you are playing aggressively the whole time. Just be the first of your alliance to be bigger than shogun.

Institutions/tech don’t matter, diplomacy barely matters, ae doesn’t matter, money and manpower don’t matter as long as you keep growing, nothing matters except eating other little dudes. Pretty fun. I’ve never played as ashikage but it’s gotta be way less fun, unless you can beat up mainlanders with your pet wasp nest.