I believe the popped button gift is at least partially a reference to Getsuyoubi no Tawawa, since one of its female protagonists, Ai-chan, gives her salaryman boyfriend one of the buttons that get popped out of her shirt from the strain of containing her prodigious bust a gift every time she meets him on Monday to cheer him up in the face of his corporate workload... and one episode from last year had Ai-chan's younger sister be surprised by how many of the boys in her grade asked her for her shirt's second button when they were graduating to a higher grade.