[Festin]

Celestrial General is quite nice, but it still has some weak points:
*)No earth bless for thugs. Boots of messenger will do the job of course, but, as I see it, the whole point of Kenzoku and Ghost General is their low cost, and this means minimal equipment (something like Demon Whip/Vine Shield, I think). In thier current state, Jomon cannot rely on thugs in midgame, because they will not have enough of them.
*)Need to empower to summon Dai Oni.
*)He does not help to get underwater.
*)He is quite expensive. With their non-sacred mages, Jomon likes good scales.

I think I would try to do something with Ghost King, which really shows how messed-up Jomon is. Who actually uses Ghost King apart from Jomon?

Low HP thing seems a bit illogical: why are Tien Chi soldiers 10 HP then?

I think Aka-Oni Samurai are far better then other Jomon units, including archers. But archers could be very nice, hypothetically, if Jomon had reliable 2F and 2A.

Some suggestions:
1)Reduce samurai armor weight. Come on, it is ridiculous, really. Jomon infantry is not overpowered in any way, since there is an obvious counter for them.
2)In CBM, Jomon can summon Kappa commanders early on. Nice, but a bit pointless, because they are too weak to be used as thugs and have nobody to lead. Give Jomon a low-level Conjuration spell that summons several regular Kappas, or change an existing spell so that it summops a Kappa Chief and 10 regular Kappas(more expensive, of course).
3)I do not know what can be done with their mages and path access. Probably somebody more experienced can suggest something without ruining the balance.