Japanese civilians have always been very subservient up until the democratic movement beginning after ww2, i doubt there would be any civil discontent no matter how bad a war became in 1905.
Also Japanese military personnel again pre democracy have always been more willing to die for the emperor than any other nation, so a break down in discipline and morale is most unlikely.
The ones who made the decisions pre democracy were the politicians and the military brass, so the only way to get japan to surrender, IMO is to convince them with extreme violence or negotiation etc.
A defeat at Tsushima and even the loss of a whole army in Manchuria I doubt would make them fold on their own, it probably would bring them to the table but the negotiations would be hard bargaining.
As for Germany in 1918, the RN blockade was the most important factor in the armistice (the other factors obviously had an effect) but it was the blockade that that was the real kill shot, if the Germans hadn't folded in 1918 there would have been a famine of biblical proportions in 1919.
Veni, vidi, verrimus!
I came, I saw, I swept the floor!