You'd probably have to go back to the first Sino-Japanese war, or rather the run up to it, and make China put up a bit more of a fight.
Before that war things in East Asia pretty much went like:
Japan: Yo Korea, look at these fancy new train things I have, I bet you want some right? And these shiny guns! Ooo! It'll really help you keep your independence in this dangerous world. *and protect us from someone taking advantage of your incompetence to invade us too...grumble grumble*
We'll sell some to you at a super low rate if you give the contracts to a few of my guys.
Korea: Trains? Ooo. Shiny....But wait...the Confucianist texts don't say anything about trains....
Japan: Well...yeah...those texts are 2000 years old. These trains are brand new....
Korea: If it aint broke why rock the boat? It's been a pretty...well up and down, but generally OK, 2000 years right?
Japan: You've seen those Russian guys knocking around your northern border right? And those French ships? The world is changing man. You gotta modernise or they'll get you *and drag us down with you, you fool!*.
Korea: Yeah... you have a point...maybe that's an OK idea....Modernisation ey...I think I have a faction calling for that....yeah....
Japan: That's the way Korea. Remember back when you used to be cool and innovative, like with those iron clads!
Korea: Iron clads?...oh yeah...that was when.....you attacked me right...err....modernisation or......let me just check with daddy.
Japan: Daddy? Wha?...oh fuck fuck fuck.
China: Yo Japan, what's this about you trying to destabilise Korea?
Japan: Ah, nothing China, nothing at all, we just wanted some kimchi, mistranslation maybe? Heh, heh....
China: Yeah....well....you better leave it that way. Korea here is a good boy, aren't you Korea?
By the way Japan, whilst we have you here, you know we've been doing this modernisation thing lately right?
Japan: Ah, yes, of course, and very well too sir, lovely navy if I might say so.
China: Yes. Well. In keeping with that we've been examining the books and....you know, it seems you haven't been paying your protection money for the past few hundred years...
Normally we'd let it go but...modern times and all that...Can't look backwards in front of the Europeans can we?
Japan: Ah....oh, I think I left the oven on, don't want my sushi to burn! Later!
*Crap! China! That's all we need. The Russians may be bad and all but...they're new. I remember when I was a kid....China....That guy is freaking scary!*
But then war eventually erupted between China and Japan and...contrary to all expectations (opposite to all expectations even, it can't be underestimated how much of a surprise it was) China got stomped.
This really drastically overhauled the Japanese world view.
Add in to Russo-Japanese war too and the Japanese were really beginning to think they were seriously the shit. Perfect breeding ground for far right insanity to emerge once the economy turns bad.
Make the Sino-Japanese war less of a resounding victory though, maybe Japan gets concessions in Korea but doesn't pull it totally out of the Chinese sphere, and they could stick to this "We are weak and the world is dangerous- strengthen our neighbours to strengthen us by extension" view.
This. Japan's ultimate rival is China, not Europe or the US. A prosperous, modern China is Japan's nightmare scenario. Which is why Japan is currently considering amending Article 9.
A prosperous, modern China is pre-war Japan's nightmare scenario- yes.
That's why modern Japan is considering amending article 9- arrghh!!! no no no no no no no no no no *infinity.