- +10% Infantry combat ability
- +20% Galley combat ability
- +1 Yearly legitimacy
- −1 National unrest
- +10% Trade power abroad
- +20% Land force limit modifier
- +20% National manpower modifier
- +20% Spy network construction
- −10% Development cost
- +10% Institution spread
Hosokawa is the largest Daimyo in Japan, both by province size and development. This means that expansion is quite easy, especially in Kyushu, which is filled with OPM's. By taking over the surrounding Daimyo's, you can become powerful enough to unite Japan very quickly. Afterwards, Japan can colonise Australia and Indonesia, Western North America, and become extremely powerful. Otherwise, invading the Jurchen Tribes and Korea can set some quick expansion options in motion.
Your first goal should not be to unite japan, rather you should think of Japan as the entire map. Consolidating in the south is simple, though with such alliance networks, not to be taken lightly. You have enough troops at game start to comfortably annex one or two OPM's, but if they ally the larger daimyo's, such as Uesugi or Yamana then you could be in trouble. You get a free CB on all neighbouring Daimyo's, so expansion is relatively easy, especially considering how many small Japanese minors are around you. Ally's are almost always discretionary, but Shiba can be fairly powerful, and Uesugi can be as well. After uniting Southern Japan, (if you're lucky the bigger nations will end up in an eternal war with an OPM with a fort, so coalitions aren't that common to fire) you will have troops to conquer Kyoto, but you may not want to, because it's much harder to expand as a Shogun than Daimyo. Ashikaga will also now have a CB on you, so be wary. If Ashikaga (or whatever other Shogun) declares, you will have to rely extremely heavily on mercs, unless you've allied most other Daimyo's. If this happens and you win, taking Kyoto should be a first priority. You will then become the Shogun. Now you should just play a normal vassal game.
Otherwise, continue uniting Japan, going towards the north. Once you have taken all of Japan except the Shogun, declaring independence will be an easy war. You can now form Japan, and take advantage of some very nice ideas. After that, you can start colonising, and doing what Hirohito couldn't, or invading Korea and eventually China, doing what Hirohito and Meiji couldn't.
Unite Japan as a Daimyo.
Start as a Japanese Daimyo, convert yourself and all of Japan to Christianity.
Embrace "manufacturies" institution as Japan by 1655.
Go full isolationist in 6 Incidents.