“Sayonara Slam” by Naomi Hirahara (Prospect Park Books, 280 pages, $16)

In a genre in which unusual amateur sleuths are the norm, Mas Arai is in a class by himself. An 80-something gardener who was born in America but whose parents returned to Japan, Mas survived Hiroshima and can’t understand the modern world in which he lives. He’d much prefer to quietly tend his garden, visit his girlfriend and have little interaction with his daughter and her family, who live with him.

Despite his failing eyesight, Mas is an insightful sleuth, whose knowledge of Japanese culture and history plays into each case in which he’s involved. Edgar winner Naomi Hirahara’s sixth outing with Mas weaves in baseball and the aftermath of WWII in a plot filled with twists.

In “Sayonara Slam,” Mas is helping his son-in-law, Lloyd, now the head groundskeeper at Dodger Stadium where Japan plays South Korea in the World Baseball Classic. But Mas’ quiet day takes a turn when a despised Japanese sportswriter is poisoned. Mas becomes involved when he is hired to be the driver and translator for another Japanese journalist investigating his colleague’s death.

At the heart of Hirahara’s series is Mas, whose greatest mystery is how this curmudgeon tries to open his heart to others.