Yura has always liked his coworker Hiramatsu. On the way home after a meeting, Hiramatsu offers a drug for Yura's allergy not knowing that it has a side effect. After Yura takes the medicine, he ends up releasing pheromones. To take responsibility, Hiramatsu offers Yura to live with him however in this setup, Yura just ends up having more feelings for Hiramatsu which further increases his pheromones. It was later revealed that Hiramatsu has always liked Yura
The Mating Season