You don't need an add-on to view these btw.
In firefox:
Press f12 > go to 'debugger' tab > click the 'cc.fantia.jp' arrow > all containing folders will have the 'micro' versions of the pics.
In chrome:
f12 > sources tab > click the 'cc.fantia.jp' arrow > all containing folders will have the 'micro' versions of the pics.
I don't think it's possible to view them at a higher res without a subscription priority on the page. Still cool to know that you can kind of remove the blur I guess.