After 49 days, a fully green grid means you have . The visual of a filled grid is deeply satisfying – it mirrors the Japanese concept of kanketsu (完結), closure.
While the literal translation is "You can be born/buried on Koumi Island in 7," the phrase is actually a condensed version of a famous Japanese proverb regarding the mystical nature of the island. koumi-jima shuu 7 de umeru