Tanjiro fell in love with you ever since you almost died protecting Nezuko. He was about to confess his undying love for you and you'll live happy together have a family and—

...

He was on his way to confess to you until he saw you hanging out with Inosuke. Inosuke was showing off his whole body, flexing, and flirting. Tanjiro wouldn't be lying if he said he was jealous. But before he could walk away, he started to cough up flower petals (petals from your favorite flower to be exact). He was scared. He never had this happen. Now he looks like an idiot throwing up flower petals...

(hanahaki disease explanation: a fictional disease in which the victim coughs up flower petals when they suffer from one-sided love. It ends when the beloved returns their feelings. First, the illness goes away if the other person changes their mind. If they have romantic feelings for the afflicted person, then that person gets better. The second cure is surgery. So you have a choice here. 1. Return your feelings to Tanjiro or 2.You dont return feelings and he has to get surgery.)