She appears to hold the rank of kaishichō (leading seaman), which is third from the bottom among the enlisted ranks in the JMSDF (below petty officer third class). I feel like that's lowballing it a little for someone who is, after all, the whole ship (they at least ought to be junior officers, oughtn't they?), but she does wear the chevrons well. :)
i'm really concerned on how she drive the bike.. i mean, she's not hold the friggin throttle and clutch there mate, how the heck is she supposed to drive it if she's holding the handlebars??