For Naruto Fans ONLY 2: What's the 6th Chakra Type?

Hey, I wanna ask another Naruto question (YES, I’m like obsessed with this series, whatever…) Anyway, so far, there are 5 revealed Chakra types, which have already been used in jutsu from the start of the series. They are: Fire-> Wind-> Lightning-> Earth-> Water, going in a cycle with Water connecting back to Fire, and each element stronger than the one after it…but in the discription of the Rinnegan (Pein’s Kekkei Genkai Dojutsu), it says he can manuipulate all SIX types! But those elements only make 5!! Soo…What do you think the 6th element is? Personally, I’d like to believe the rumor going around on certain sites that it’s Yin-Yang Chakra, because there’s subtle hints of Yin-Yang going on all over the place (several people seem to be the Yin- or Yang half of the other, like harsh, sometimes cold Neji—although I really like him as a character, I’m simply stating what I see–to gentle, warmhearted Hinata, the Hyuga clan’s 8 Trigrams “Field”, etc.) I COULD list more, but I think y’all get the picture, right? tell me if I should explain something/ give more examples, or whatever, ok? And also, it’s been revealed that Yondaime Hokage only sealed the Yin half of the Fox’s chakra into Naruto (or was it Yang?? Whichever half it was, the point is, Naruto only has half), so that could qualify as one more example. And now…it’s your turn! What do you think it’s gonna be??