[Slobby]

Only comment I have is that Jomon should aim to get a sea province asap (something you omit).

Ryujin and the shark warriors may be the best thing that Jomon has going for it.

Easiest way into the sea is an awake Wyrm. I just made one dom10 neutral scales E3, but A3 is likewise doable and then you have your guaranteened arrow fend/mist caster and with a little finesse storm caster who can cloud trapeze around to support your armies. The Wyrm will also aid in expansion.