Ok, can we just take a minute to appreciate this animation sequence? No, seriously. This is how boobs work! Too many animation teams seem to think that breasts somehow defy gravity. They don’t. If you take away their support; they fall (to the sides if you’re on your back - as shown here). Well done this team. Well done. =)
As a girl with natural big breasts, I can confirm this.
Realistic boob physics in anime are always welcome on this blog