I think the most important thing to think about is how your waifu would feel. Do you maybe feel like you're cheating on her because putting Rei on your second monitor would bother your waifu? That's the basis on which I try to decide these types of things.

Post edited on 8th Jun 2015, 12:11pm

personally, I think you're making too much of it. A good comparison would be someone hanging out with female friends when they have girlfriend. that's not cheating because of the feelings that you have for them. If you have romantic feelings towards them and you feel it is wrong then I would relate it to cheating.

I don't see anything wrong with it. Heck, if anything, in my head they're meeting and hanging out, becoming new friends, and the like. My waifu is a magical girl, so meeting Madoka and co was a trip and a half.

>>18442
>Heck, if anything, in my head they're meeting and hanging out, becoming new friends, and the like.

This, my waifu is not a vocaloid but I do enjoy listening to Hatsune Miku and Gumi, I do acknowledge such vocaloids are cute and thier music is good, but the feelings I have for my waifu don't even come close to what I have for them.

It used to bum me out that I'm spending time listening to vocaloid rather than my waifu, but I realized my waifu can enjoy such songs too, then I imagine us both sitting together listening to Vocaloid, talking about the songs, and even dancing with them toghether. Same logic applies with movies, video games, etc.
Now I don't think our relationship could get any better, but you never know, the more I spend time with her, the more I'm surprised.