You should only do what you're comfortable with. I personally love it when my boyfriend touches and massages my breasts. My boyfriend says boys like touching girls breasts because they're soft, fit in their hands, and they like it when your nipples get hard. Be warned though if you let him touch your breasts he may want to go further.
they say guys are addicted too breast,but this is the other way around.
More How A Boy Touch A Girl Chest images
Answer: Because the social norm ATM is that a girl’a chest is a private area, so we, as decent human beings, respect that. A more accurate comparison is if people are allowed to touch boys’ penises, why can't people touch girls’ bare breasts?
Touch has an almost intoxicating effect on the human body. A woman runs her hand through your hair, then softly touches your chest before kissing you. A bolt of electricity shoots down your spine, and you feel wonderful as a wave of oxytocin courses through your body. Touch expresses your intentions and desires in a way that words cannot.
Using boy mannequins during the trial, Clancy showed how a large adult hand placed on the center of the chest nearly touches the nipples on a small boy’s chest without moving.
Tripp's Tension Technique - http://www.trippadvice.com/tension-techniqueWhen you can break the touch barrier with a girl in a way that doesn't come off weird...
When a man touches your chest area, he may move his hands higher and lower down your body. If he decides to grab your breasts and squeeze them, this is a very erotic act. However, you should let him. When a man touches your breasts and starts to massage them, he may use his mouth. This is not a soft thing, which means that your man may push against the breasts to get them stimulated.
Touch his chest. If you want to be flirtatious with the guy, you can place one hand on his chest as you're talking and moving closer to him. This is especially effective if he's standing with his back to a wall or if you're in a small, enclosed space. 
RICH kid Grisha Mamurin has provoked a storm of protest by paying girls to flash their boobs in public and then to kiss him.