I'm about to crash my head feels like lead...(i did spell that correctly right? it's the thing that can poison you)... um spice and wolf is probably the most mentally engaging anime I've ever watched, it's about a wolf "God" who dwells in wheat and watches over the harvest of the town near the field, but as the town progresses into different times the need for Holo dwindles, so she sets off with a peddler in order to go back to her homeland.
Totally agreed on the mentally engaging part. Other than the "Wolf God" part, the anime is super realistic as well. And cause it displays the time in which it plays so well, it becomes super engaging to watch. (thanks to the story too, though.) -nodnod- ... Plus Holo is awesome. ^.^