According to THIS guide by binary, it's "for IR connection to some other devices: the "Heart DekaTama" (located in the TamaDepa store in Tokyo), and the DataCarddas "Fushigina Ehon" (arcade game in Japan.)"
According to THIS guide by binary, it's "for IR connection to some other devices: the "Heart DekaTama" (located in the TamaDepa store in Tokyo), and the DataCarddas "Fushigina Ehon" (arcade game in Japan.)"