canada is built of immigrants but people have to remember, some of these immigrants have a lot of mixed blood already.
the most likely scenario is one of risako's parents is most likely 3/4 japanese and 1/4 something else, prolly from one of the european countries. so she is mixed in that way.
with risako's grandparents, you have to remember that she has 2 sets of them. one of the grandparents could be a non-Japanese