Talk about being introduced to Japanese.

Add in reasons why you had intrest in it (nothing but anime but more like, "I thought the art of the Ainu culture was beautiful and very previalent in the dress of edo and pre-edo period Japanese society" or something about the spoken language and the written).

Talk about you first classes and beginning to study it.

Talk about why you want to go to Japan (mostly about improving your Japanese proficiency but also about being immersed in a different culture).

Talk about what you are going to accomplish there.

Talk about how this will help your university and their relations with the one(s) in Japan.

Talk about how this will help you as a student of their university (become a better student) and a better graduate (more cultured et cetera..).

Kiss ass as much as you can.

If you having gotten at least a 3.0 avg in all of you Japanese classes I would say your chance is low. I have written two of this type of essays to go on exchange at my university (University of Alaska Fairbanks) and I was denied both times but only because my overall gpa was too low. Don't make that mistake and make sure you have a good overall GPA at least 2.5. A 3.0 would be better for a Japanese college to see but might as well try. Look over all the requirements and all that too. Also, get a passport in advanced because they take long now a days (thank you DoD and Homeland Secur).

Good Luck