Yandere Male x Male Reader

Prologue

(A/N: This is the boring part of the story)
Thinking back, I don't even understand why I became friends with him. It was always a mistake, since the very beginning...
When I was around 6 or 7, I had moved. I was nervous going to a new school, and wasn't sure what to do. So, when another kid came up to me and started talking to me, I naturally talked back. I needed to get some fiends at that time, but still, I don't get how he and I got closer to each other. His name was Kousuke, and somehow he was a bit weird. He didn't really act like other kids, and I always felt like he was hiding something. It was only later that I figured out why. He had some problems regarding his family, but to make things short and not to think about that, he ended up later living with his aunt and uncle.
The main point is, he wanted to stay friends with me, and continued being my friend for many years. The thing is, he was always clingy. Not just affectionate, but really affectionate. However, when we entered high school he got worse. He always wanted to be with me. He always wanted to know what I was doing, or who I was talking to. He didn't want me being with other people. I don't know why, but he seemed to hate my other friends, and talked badly about them. Saying how he's better than them, and that I should only be with him. It felt like I was tied up in chains. My freedom was taken away from me. I couldn't take that manipulative attitude he had.
So, I made a choice. I stopped being friends with him. I put distance between us, talked to him less, and avoided him more. I didn't pick up the phone, and ignored him at times. My tactics of getting away from him were succeeding, and before I knew it, we were already so distant from each other. What used to be a long lasting friendship had crumbled. I was freed at last. I could finally enjoy myself. That's what I thought back then.
Now, he sometimes still tries to start conversions with me, but I don't comment much or at all. Just like today.
I walked into school with a bored expression, ready to fall asleep at any given moment. Then Kousuke spotted me.
"Good morning, (y/n)"
"...Good morning, Kou" I lazily said without thinking much.
Ah, did I just?
I saw his cheeks turn a bit pink and his face was debating whether to show a smile or not.
As a nickname, I always used to call him Kou, and I still can't completely get rid of that habit. I try not to call him that so that we're more like strangers, but sometimes I let it slip.
Before he could say anything more, I walked away to my classroom. Luckily I didn't have class with him. What I didn't notice was the way he looked at me while I was walking away. With those red, menacing eyes.
That's when I heard a girl whispering about how she just passed by Kousuke. Kousuke is good looking and people talk about how he looks hot, or how he's nice. However, no one goes up to him or talks to him because of his personality and the way he acts. He just doesn't want to talk to other people. So why does he try to talk to me?