I've determined why you couldn't declare war: Your annual income is 947 gold. You only have 396.5 stockpiled.
A Claim CB would require at least 475 gold stockpiled, though will only cost 95 gold.
A Conquest CB would require at least 947 gold stockpiled, though "just" costs ~250 gold.
De Jure Claims don't have gold stockpile requirements so far (an oversight of sorts... or not

), but you've pretty muched conquered your de jure territory anyway.
So in other words, it's your own fault. :laugh:
Granted, I might need to reword the starter events to reflect this (I haven't fixed, well forgot to fix, the typos you guys were referring to btw)
in any case, you owe me beta-testing time. After all, you stole some time that I would have spent watching Date A Live!
(tsundere Tohya ftw! :3 )