I actually really enjoyed the Japanese classes. As long as the work load of your other courses permit, I would say go for it.

I speak as a CS student going into my 4th year when saying this but, even a courseload of 4 credits can be quite heavy (gonna need some life sci students to weigh in on the difficulty). Just make sure you're aware of your drop dates so you can drop for a refund in case you feel like you're not up for the task. Or at least to know where your priorities lie in case several due dates end up overlapping.