The Japan Post has a special Summer Postcard system (similar to New Years Cards). It is called kamome-ru (“kamo mail”). It is sort of a play on words, since kamome かもめ means “seagull,” and me-ru メール means “mail.” So the impression is like seagull mail.
On the bottom, lottery numbers are printed, the time period of sending these postcards started in June and will end August 26th. The winning numbers will be announced September 6th.
Yesterday I received some kamo-mail from one of my older students. Such a kind thought. She writes in Japanese very carefully and clearly so I can read it it easily. I will be sure to check the lottery numbers when they are announced… !