Answer:
Repeated twice, the lyrics are transliterated as:
Kimi ga yo WA / Chiyo ni yachiyo ni / Sazare ishi no /
Iwao to nari te / Koke no musu made.
English translation:
May the reign of the Emperor continue for a thousand, nay, eight thousand generations and for the eternity that it takes for small pebbles to grow into a great rock and become covered with moss