Your mentor and teacher Toshinori Yagi has been suffering with a condition known as Hanahaki disease, which makes him throw up flower petals. It came on slowly over time. At first, he would cough up a petal or two, but then, he began to throw up multiple petals at once. It turned out, he was in love with you. It was a fatal condition unless the person he loved returned his affections. So, one day, you heard him getting sick in the bathroom, and you immediately knocked on the door.