There are three misunderstandings happening at the same time, god damn! I have never seen so much misunderstandings at once!
1. Yuanzi thinks Yu is going out with that guy
2. Everybody thinks that she is acting this way cause she lost her painting (half truth)
3. Yu Qi thinks Yuanzi is only upset because she is missing something
Ya know? There is literally one very, VERY simple situation to all of this, sit down, AND FUCKING TALK! XD