Kyou mo Ashita mo Warabii-sensei

One day, a Japanese professor on a field expedition to Australia has the surprise of a lifetime when a wallaby suddenly falls on him from the trees above. The wallaby is slightly put out (as he explains quite calmly) because, you see, he was distracted while reading a book about one of his favorite subjects—bushido. He's a bit of an otaku and has always dreamed of going to Japan. The professor is instantly charmed, of course, and whisks Mr. Wallaby off to Japan. Mr. Wallaby, inspired by the professor, says he also wants to become a teacher...

(Source: Kodansha USA)