PEORIA, Ariz. — Miles Mikolas has parlayed his three-year stay with Yomiuri in Nippon Professional Baseball into more than $49 million guaranteed. Merrill Kelly, Chris Flexen and Pierce Johnson, too, are among the arms who’ve breathed new life into their careers in either Japan or Korea. So Nick Martinez was certainly hopeful as he passed on a number of split contracts to pack him and his pregnant wife, Kimberly, off to Sapporo, Japan, in 2018. Yet he’d largely treaded water with the Hokkaido Nippon Ham Fighters until the pandemic enticed him to truly look inward for change. “It’s kind of hard…