Reader's discretion IS advised!
This will include sensitive topics such as homicide, suicide, gore, and more. Including mental and physical abuse. This goes to both genders.
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Danger lvl: 10/10 or 14/10
When he first laid his eyes on you, he immediately thought you two were meant to be. Like any typical Yandere.
Sanemi ended up becoming a walking happy dog when it came to seeing you or talking to you. Always managing to keep up a conversation and just not acting like himself. This brought up suspicion within the Hashira and Kagaya Ubuyashiki.
He seemed like he had a lot of confidence while just talking to you. That's when his stalking started to happen. His absence at the Hashira's base ended up becoming more suspicious behaviour. Nah, he kept claiming he was on the same missions as you. Very likely this was strange to you but as a demon slayer; you didn't question it. Having a Hashira around was nice as backup.
Surely this couldn't end up as something worse, right? Even though, last you checked, he originally didn't give a shit about you. The sudden change after a week was a shock. Shinobu gives you several warnings, though. She noticed his behaviour and tries to keep you safe.
(If you take her advice, it's likely you dealt with Sanemi by telling Ubuyashiki about his creepy behaviour. Just do this before he gets worse. Feel free to read forward though!)風 Stalking 風
It gets worse. You didn't notice for quite a while. So, Sanemi chose to experiment. How close could he get to you without being spotted? Apparently he can stand just a few feet behind you without being spotted. Remember, he's a Hashira. He's pretty quick (not as fast as some other Hashira's).
You sometimes swore that if you turned around, you saw Sanemi. But with as fast as you saw him, he disappears.
His stalking only grew to be worse and worse. If he wanted to talk? You two 'conveniently' bumped into each other at 'surprisingly' the same place as you. Or he could've been right behind you without you knowing. He sometimes appeared at your places. Sanemi got to the point on taking some of your stuff. Yet you couldn't find said stuff. Not even when you went to his place.
風 How long can he go without seeing you? 風
Never. He can't go too long without seeing you. If that wasn't already obvious with the stalking part.
You're just too cute to him. He sees something he likes, he has to come in and take it. Right? That was his logic.
So, pretty much he can't do so well without you there. (Read as: he's obsessed.)
風 Yandere Type? 風
He's the elimination kind. Someone bothered you? He kills them. Someone said they had a crush on you and wanted to confess? You're his, not theirs. You likely found him covered in red before after he got through disposing of a corpse. He just says he got red paint all over himself.
風 Kidnapping and what he does 風
Very likely terrifying. Imagine being tied to a chair in his room as he sleeps with you there. If you beg enough to lay with him, let's just say... You get to sleep with him during the night, just moving to leave will wake him up. Unless he's having a night of deep sleep.
He's willing to do ANYTHING for you. Except for letting you go. He'll cook for you, let you wander his room, etc. once he trusts you enough though, he doesn't mind letting you roam his house. As long as he gets to come with you to the stores. Unless you want a bath/shower and to use the restroom, then take as long as you need. It's probably the only way to get away from him.
He also buys you gifts and stuff for you. All the stuff he gets you though are things he knows you'll love or stuff that you said you wanted. At least he pays attention.
Oh, don't worry, he doesn't raise a hand or his voice at you. He doesn't mock your freedom in your face, either. His manipulation skill is low though, so he doesn't manipulate you.
風 If you run away + if you pass 風
Running away is going to kind of be hard to do, my guy/girl/whatever you are. Sanemi is with you everywhere. So you need to escape through the bathroom or somehow lose him while shopping. Physically fighting him isn't going to work since his muscle mass is large enough to overpower some.
If you succeed in getting away from him; he goes fucking ballistic. Deaths are happening left and right, this man doesn't care anymore. He's out to find you. Even if it requires killing others or even you.
When he does find you, he is covered in crimson and looks like he lost all his sanity. Now he probably does look scary in this moment but he'd hold you close (to his blood soaked chest) and ask why you left him. How could you do this, yada yada. If you push yourself away from him? You're done for. He ends your life with no hesitation.
Soon after, he'll take his own life.

YOU ARE READING
☪𝐃𝐞𝐦𝐨𝐧 𝐒𝐥𝐚𝐲𝐞𝐫 𝐇𝐞𝐚𝐝𝐜𝐚𝐧𝐨𝐧𝐬 (𝐎𝐋𝐃)
RandomHi and welcome to my Headcanon book for KIMETSU NO YAIBA!!~ Or better known as Demon Slayer!! SPOILERS AHEAD (IN THE BOOK)!! Some of these may already be Canon but I might not know that, bare with me. This may also get slow updates compared to my Un...