While it is usually Kaito that gets bullied, he doesn't have much presence in these comics. The next in line is of course Len, who we regularly see being bullied by Rin. Add to that his likeliness to offer to carry Miku and Chibi-Miku's stuff in the vain hopes of getting her attention. It seems that nobody is really bothered enough by it to help him out any. Poor, poor Len.