Some people regard use of cleavage as a form of feminine flirting or seduction, within the confines of community, peer group and personal standards of modesty, as much as for its aesthetic or erotic effect. Many women use cleavage to enhance their sexual attractiveness. Some people derive erotic pleasure from seeing a woman's cleavage, some derive pleasure in their female partner's exposing her cleavage, and some women expose their cleavage for the pleasure of their partner.
Credits to wikipedia!
Well,after reading the definition of this word "Cleavage",i guess more interest grown on you guys to watch the video.To be honest,this is the very first time i have ever seen Yuri showing her cleavage,but of course she accidentally showed it,or to say that i am evil,i would just say that i am a good observer,kindly pause at 4.17 to watch the interesting scene!