That child (Yuki's friend) is difficult to like and understand

I think he's rather easy to understand. Yuki has kept secret that he in fact feels completely imprisoned, traps and desperate for just a bit of freedom. His friend actually thinks Yuuki LIKES being so 'perfect'. because that's all he's ever know. So he thinks this transfer student has come just to completely mess up Yuukis life and change him. makes sense he would try to protect Yuuki.

Yeah.. no.