Planned, she was on her period so we bought some lube and decided to try anal. We spend more time that we'd like to admit adjusting the amount of lube and stimulating her ass until I could penetrate her asshole. But the sensation was awesome for both of us. She always says the insertion is painful, but the sensation of my dick ramming her asshole is amazing. While we haven't made anal our "main" form of sex, we like to do it when we feel adventurous or when we can't use her pussy. She's always afraid of the insertion, but loves the fucking once my dick is inside.