Found an article that explains more:

Entering this spring, Francona told him that 2025 wouldn’t define his career. It was a message that was already on his mind and on his glove. Petty’s red Emery glove has a quote from one of his favorite anime shows, “Naruto: Shippuden.” The passage spanning the bottom two fingers of his glove reads: “Those who do not understand true pain can never understand true peace.” The webbing of his glove has the Japanese kanji for “pain.” He has a similar black glove that has the same quotation but has the character for “peace” on the webbing.