Shinzo Abe stated during a speech entitled "Japan is back", the following line
Now, if you look at the lapel of my jacket, I am wearing a blue-ribbon pin. It is to remind myself, each and every day, that I must bring back the Japanese people who were abducted by North Korea in the 1970s and 80s. Among them was a girl, Megumi Yokota, who was only thirteen at the time.
The Chrysanthemum flower on the red background is the symbol of a Minister's role on the Japanese Diet.
NOTE the second link above is broken, so while it doesn't really explain this specific pin, I'm including a wikipedia page which explains a bit.
NOTE Shinzo Abe was killed today, 8 July, 2022, in Nara, Japan. It was suspected to be a targeted killing by a "dissatisfied constituent." Abe was the longest serving Prime Minister in Japanese history. The killing happened while Abe was on a campaign stop.