Hey dude i will give you some advice that worked for me , as i noticed you must be atractive. All the posts that our dudes say here are true but the thing that you can do is, Make a situation where you will be naked standing in front of her! Example: Sis comes by , you go to shower dont close the door completly , take your time with showering , if you are done just be naked in the bathroom and make something (take your time) the reason is to get her eyes on you when you are naked. If she comes and see you so just w8 for her reaction or say something like "hey thats not for free" or turn around facing her and say "What you think? " its sounds very crazy but its nothing she can do with it. If your GF is at home to that time do that and dont go further than that, you have opend a door just now.
Why i am telling you to fuck her? cause mate you will get crazy believe me you will. The good parts are that your gf believes you has trust in you and you can manipulate her , as i realized from your posts.
So if you have done all that with the bathroom or a similar situation, he will either get shocked because she wants you but she never thought she can have you or she will fuck you. So just go in her room at night or when your gf isn't home and say " Hey i hope despite what happened back then. you are still comfortable around me" propably she wants you and will say something like "why not? or of course" or some shit like that so if that happens... man the other stuff is easy just think about it.
But the hard stuff is to manipulate her, so she never says your sis about that! so How about to be THE MAN! like hey if you want more you will keep your fucking mouth closed ( i will not say guide details here).
MAYBE she tells your sister the only thing that you have to do is preparing for that with a godd excuse that you werent home all the day , involve some friends to confirm that etc. etc. etc. after that speak to your gf and say stuff like "you know thats not true" , " i told you about the naked/changing thing" , " and because she cant have me she told you shit like that to get us appard, that was the only reason she maked it and blablablalba" i think you got the idea

Have done it all what i said here and it worked 100% , you need to be a good actor and you are.

The Greek

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I am not a PUA! All my writings are my opinions and experience.
If you need a wing LONDON just pm me.

Alternatively, you could try not being a dick.

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One cannot lose what one has never had.

Wow. There's the rubber stamp. If the OP values his relationship with his girlfriend and wants to stay together you will not follow this advice. Mark my words. You are opening a can of worms and creating a huge problem for yourself if you listen to this. Inviting bullshit into your life is not game.

if you are even thinking about doing her you are not respecting your relationship already. if i get ideas or thoughts about other woman i might as well end the relationship because if i really loved her i wouldn''t think about other woman.

im really a relationship guy . i would end the relationship... however i really would fuck her sister in the process LOL and after that i would really try to work on my inner game for being heartless lol

lol i might as well release you from your misery.... i give you permission to fuck her sisters brain out , just tell your GF Lodewijkp told you to do it !

another solution is to hook up her sister with another guy....maybe the best solution...

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AK-47...When you absolutely positively have to kill every fucking orc in the room
questions about herbal medicine here-vp582526.html#582526

I think it is normal for Gf sister to change in front of you. Has happened to me few times. Also GFs sis walking around panties etc

Btw I fucked one of my GFs sister

Be aware, It also might be trap!

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Still learning