My plan for the first part of the turnset was simple - quickly regroup, then hit Toku with two stacks (one moving along the coast, the other through the interior), force him to capitulate, then rush my troops to the other end of the empire to invade HC.
Now I know that many players baulk at this type of strategy, but I had several reasons for adopting it:
1) Many of Toku's cities were utter junk, only worth having for the resources they claimed. Vassalising him meant I could have the resources without the maintenance costs. And that, in turn, meant I could afford to expand elsewhere. Had I razed the cities, then Darius would've taken those sites, making him stronger in the long-term.
2) Vassals count towards your power rating (as far as AI civs are concerned), making it easier to vassalise the next guy. My intention was to do the same to HC as I did to Toku - take his good cities for myself, and leave him with the junk. Depending on how things had worked out, a rolling vassal/conquest victory might have offered a swift conclusion to the game.
3) The quicker I could end the war with Toku, the quicker I could get my army over to HC, hopefully hitting him before he managed to get Longbows online. In any case, I was pretty sure I'd have enough troops to take the cities I wanted.
4) From what I could see, the two principle threats on this map were going to be KK and Darius, each having access to a decent swathe of quality land. Normally, these would be the guys I'd look to take out early. But thanks to the distances involved, this wasn't an option. However, by invading HC, I would open up KK as a target for the next war. Meanwhile, having Toku at my back would give me a decent buffer against Darius, should the latter get any funny ideas while I was busy in the east.
5) HC already had the Pyramids and, a few turns into the round, he picked up the ToA as well. Plus, he has the holy city for what looks like the only religion on this continent (no shrine yet, though). Add that lot to what we already had, and the game would be all but over. Indeed, I seriously considered going for HC straight away instead of Toku. But I reasoned that, with most of my troops already in position, the Japanese would crumble quickly enough. And I certainly did not want to risk Darius taking Toku as a vassal.
Unfortunately, I only got as far as vassalising Toku before my PC died. But everything was going very much according to plan at that point. Here's what happened in those sixteen turns:
Techpath: MC -> Feudalism ->Aesthetics -> (next: Literature)
Going for MC was a slight mistake, as I could've got it in trade. I wasn't to know that, though, and my reasoning was that forges would be very helpful, giving +2

once Toku's gold was secured, while the hammer bonus would feed into my masterplan very nicely. I was also hoping to grab the Colossus (trading for copper from KK), which would reap considerable benefits, given the amount of seafood I was collecting.
At the time things went belly-up, I was unsure whether to go for the Great Library, but I reckon I could've grabbed that after the Colossus, given the awesome hammer output of the capital. In any case, I wanted access to the Heroic Epic, and hopefully to grab the Great Artist from Music for a Golden Age to steady my overstretched economy later in the round.
I set the cities at the extremities of the empire to build courthouses, but everywhere else kept pumping troops. The GG was used to create a Medic3 Chariot (which also picked up Morale during the war), to speed the turnaround from Toku to HC.
Ten turns into the round I declared on Toku, and sent one stack along the coast to take Izumo and Nagasaki, while the other went for Satsuma via Kagoshima. The war lasted a grand total of six turns, and all four cities were captured without a single casualty (the only unit risked at less than 50% was a disposapult which survived attacking Satsuma at 13%).
My last act, before shutting my PC down for what I now know may have been the last time, was to take Toku's capitulation, gift the useless Kagoshima back to him, and demand a supply of Gold to keep my citizens happy.