There are two manga I would like to find but my memory is extremely partial this time.
Hopefully though it will be enough.

1. There is a guy and I think his weapon is a sword? He is trying to get revenge on another guy (who is maybe a supernatural being) because he thinks that dude has done some kind of great wrong. However it turns out he hasn't but the supernatural being had personal reasons for concealing the truth. And the supernatural being definitely makes romantic advances on him whenever he comes to kill him...I think.

2. The main character starts to fall for a guy. This guy is an aquaintance of his sister and his sister has always thought of this guy as innocent. So when she stumbles upon the truth about their relationship she immediately thinks he has attacked the guy whereas in fact it's the other way around and he says to her something along the lines of 'the one doing whatever he wants is this guy,' much to the sister's horror.
   I also remember a scene where she says her yaoi manga are part of her fantasies.

Lol I remember the weirdest things about manga sometimes.

Anyways, I hope you guys might know what these are.
Thanks~

Is the second one Mousou Elektel?

Wahoo, that's the one! Thanks very much ^^

Now for the first one, I knew this one would be difficult, I'm actually beginning to wonder if it even exists...

*edit - BINGO! Found the other one I was looking for - it's Honoka na Koi no Danpen wo chapter 4!! I knew I couldn't have dreamed it up!