Mangas aren't real life. Real life and real people are complicated so it depends on the person.
Now, if you're asking why lovesick characters sleep around, that's because sex lets out pleasure hormones that make you temporarily not feel miserable anymore, hence "sex to forget".
Personally, I can't stomach having sex with someone when I don't have feelings for them. So, even after a break up, I'd be super sexually frustrated because of the lsck of constant sex. But the thought of casual sex makes me want to vomit.
I actually looking for someone that have knows what I'm thinking. And I found you. But then again we have different opinions.
Really? What's your opinion?
Well pike your said in your previous comment I cant stomach having sex to a person i dont have any special feelings. Especially if we were not aquiantance at all.
I love the flow of the story. But serious question can you really forget your feelings to someone just by having sex to various people? Because I read many mangas like that .