So to start off i joined playing this campaign in the middle of eu4 japan then was a mess only propped up by near endless amounts of gold from China, Khazaria, Latin Empire, and Leon. Korea held roughly 50 percent of the home islands. I joined the campaign with zero expectations to survive and expected myself to be playing a colonial. Many wars later and were one of the stronger supporting powers in the game who influences the whole of Asia with our actions.
Session 1 Victoria
Being Japan comes with some very serious advantages and some very serious disadvantages. advantages being - we have a natural barrier of entry saying your navy must be this large for you to even touch anything worthwhile in my nation. Disadvantages being without being the worlds premier power i struggle to influence anyone that isn't an island nation.
anyway our first session went as such we encouraged clergy and set up a baseline of factories in our nation as well as foreign investment to make sure we keep great power status, sphereing 3 nations of Kimifornia (California), Australia and new Medina (new Zealand). the worlds premier industrial power and the number 4 gp.
Funnily enough it wasn't an entirely uneventful session as there was a crisis featuring myself and Scandinavia over the colonization rights of Siberia. Needless to say he ignored my warnings and lost 25 prestige after being backed by no one.
looking towards session 2 we have India opening up as well as kong and the other African minors so were gonna have at least some wars start. negotiations are underway because no one wants to fight a war. its looking to be a very peaceful Vicky but we all know it wont end that way, to many grudges and to many talks always leads to world wars. i expect the first great war to be started in America over the vast oil reserves that will be found there. one maybe 2 great wars in Vicky started over trivial things, but who knows we may see peace in our time.
There are a few treaties going on that have far greater implications than anyone is willing to admit deciding the fate of the coming wars. one for Africa and the other dividing Asia. we shall see if these are upheld or not but japan has one goal and that is to survive as a strong power preferably keeping the number 4 spot on the gp list. if we cant maintain number 4 stay a gp and all else failing live to see the hearts of iron phase.
here are our session 1 territorial gains all through colonization:

new Zealand

Siberia