Guilt

GO READ BOOK ONE: Dying Love (BakuKiriKami)

Kaminari realizes he's fallen for his two best friends, Bakugou and Kirishima, but it's more than just crushing on them. He loves them, he loves them so much he forms a disease called Hanahaki, a disease that results from one-sided love.

He gets the surgery after a near-death experience and forgets about Kirishima and Bakugou. Meanwhile, Bakugou and Kirishima finally realize that they love Kaminari back.

Now in an unfortunate circle, Bakugou and Kirishima both have hanahaki, because now they are in love with the electric blond.