You and katsuki are dating,

The girls and you were talking to eachother in the common room , the topic went to you and katsuki , they were talking about how you both love each other and if katsuki fear losing you or not , you were also curious about it so everyone made up a plan You will prank on him and see if he really fear losing you or not .

So you went to katsuki's room and saw him laying on the bed reading manga, K- hey dumbass , what happened? He asked.

(Tell him you are diagnosed with cancer , make it sound real )