hello morgana!
well, i've been really into embroidery lately..it's easy, non-permanent (if you get bored) and makes pretty much anything unique. what i'd do first is take off the eastpak logo..i just peronally hate logos, and that space is just waiting for something cool and interesting to go there. you could embroider whatever you want there...i like birds and abstract weird things (hee) but anything would be so pretty...a heart, a star, something simple, something complex (depending on your embroidery talents..mine are pretty nil) or you could just iron or sew on an applique. what do you mean when you say japanese street style? is there something specific you have in mind?
hope this is helping...