I wouldn't really count kissing someone else as cheating, unless you two made the decision together that you wouldn't do that. However, my views are that if you can't agree to the terms of the relationship you should exit it, in order to avoid something more painful that could happen down the line.

I'm gonna assume that your gf and you have the standard agreement on cheating. In your situation, if you kissed that girl back then it was cheating. If your gf was kissed by a guy and made out for a bit with him, would you rather her tell you or keep it quiet?

I don't consider what swingers or couples who like threesomes to be cheating because it's mutually agreed upon but I wouldn't say that is wise for most couples or good for the relationship. I'm completely against normal secretive cheating.

Like i said in the Kill or be killed thread the guilt would destroy me. As for if someone cheated on my you are out, i don't forgive serious breaches of trust ever.

Trust is the very foundation of a relationship. In my opinion, if someone breaks that trust in such a major way, then the other person would only be hurting themselves if they remained in said relationship.

What you did was cheating, alcohol or not, drugs or not.

Alcohol does not make you do anything, it just relieves inhibition so that you will do what you want to with less forethought.

That said, I have been in situation where I was kissed, and have returned said kiss at the club while on a wild night of drinking. This has happened twice and each time I let my GF, now my wife, know about it the very next morning when I remembered what happened. She was not happy but was able to forgive me. In the end the honestly of the situation has made our relationship stronger but it did make things rough for while.

I say you should tell her about. Do not tell her you did it because of the drugs/alcohol but you can say "While I were drunk I did this, and I am not saying being drunk is an excuse I am just telling you the circumstances." From my experience being forward like that in all situations in life will help you more than trying to cover up what was done. You do get rewarded for being accountable for your actions in life, even if immediate repercussions are not always positive.

I've been dealing with myself. My relationship isn't that great at the moment. I've gone from 265 lbs to 184 is 9 months. Lots of people I work with at my new job tell me how attractive I am, and give me plenty of attention. I don't like the idea of cheating... But I certainly like options.

It sounds dumb but you either tell her or break up. Do you want to spend the next 80 years with her knowing she's spent her whole life with you about this knowledge?

If you want to stay with her, then tell her and see what happens if you never want to tell her, leave her.

Just don't cheat in video games and all will be swell...

I agree with the above.   Add to that the fact you tried to sweep it under the rug and your relationship is probably over.  At this point you can either try to come clean as others have suggested or roll the dice and see if she never finds out (provided you can continue to live with it)

I do have to say though, in hentai I do like netorare quite a bit.