you're his coworker, who he to fall in love with. But he knew that you wouldn't return his feelings back because you're so focused on being a A pro hero, and he did as well. He didn't want to force you, or even tell you about his feelings yet

one night, you realized he haven't showed up to work all day. You dismiss yourself from your patrol and started to go to Keigo's apartment to visit him. Once you opened the door, you saw him coughing up flower petals and blood.