Ghost!Izuku whose body is invincible for the rest of the year and can only manifest during Halloween. Only Werewolf!Katsuki notice him outside of Halloween due to his high keen of senses. When Izuku discovered that, he stuck around Katsuki all the time (much to Katsuki's dismay.)

When it's finally Halloween, Deku often goes to the town to meet some of his friends (aka the people he stalked). Katsuki always feels relieved at first, thinking that the nuisance is finally gone.

He spends the time doing things that he always swears he wants to do without Deku watching his every move.

In the end, he gets upset because how dare that nerd bother him for the rest of his life then suddenly decides to leave to some extras when he finally got a body?!

And he'd rather die than admit that he felt hurt when Izuku chose to spend his limited time with someone else. He already knows from the start that the nerd only stuck around because /only/ he can sense him when's he doesn't have a physical form.

But he finds himself thinking 'Does that mean if there's someone else who can sense Izuku the same way as he does, would Izuku rather be with them?'