Basically, what Mu Siyun did was putting fuel on fire to Ding Yuan since eldest princess was having fun with him and send her photo to Ding Yuan which irritates her so much.
Oh, that stupid trash yellow hair son is just trashtalking to Mu Siyun while the teacher said otherwise since she is wiseful and logical on her way of talking.
Why we dont put him in frontline instead sitting there??? I bet he will died 1st or shit his pants and say Mommy just for that.