& daylia, the philosophy of kendo & aikido are not so far apart; in aikido you do not attack pre-emptively, but when you are attacked you generally defend by throwing the bad guy or immobiliziing him with a joint lock, & that would be an attack if you had initiated it. You don't just stand there and block.
The techniques of course are far different.
Aikido is partly based on Japanese swordplay, though not kendo. The Yagyu school, I believe, though I know nothing specifically about it.