SEATTLE — The way Sean Manaea has been pitching, it’s easy to imagine him starting one of Oakland’s first two games next season. That would mean he’d pitch in Japan.

It could also mean his older brother could see him pitch in pro ball for the first time.

“It’s awesome. My brother lives over there right now,” Manaea said. “That’ll be something really cool if he’s able to go to that game and see me play for the first time.”

The A’s and Mariners will open next season in Tokyo on March 20-21, Major League Baseball announced Tuesday. Manaea’s brother Dane, who’s 28 and two years older than Sean, is in the Navy and stationed in Yokosuka, which is 28 miles from Tokyo as the crow flies.

The last time Manaea’s brother saw him pitch was in college. As an Indiana State sophomore, Manaea pitched at Purdue, where Dane was attending.

Manaea was the 34th overall pick in the 2013 draft by the Royals, who dealt him to Oakland in July 2015. This is his third season with the A’s and by far his best. He has a 1.03 ERA in six starts — one of which was a no-hitter — and will pitch Thursday in the series finale against Seattle.

The A’s and Mariners opened in Tokyo in 2012, marking the start of Oakland’s three straight playoff runs. The A’s also opened 2008 in Japan against Boston. A trip in 2003 was canceled as a security measure after the U.S. invaded Iraq.

Both of next year’s games will be considered A’s home games.

“It’s exciting for us,” manager Bob Melvin said. “The trip we had in ’12 couldn’t have been better for a team that had a lot of guys not play together before. Culturally, it’s incredible. You learn about Japanese baseball, and you bond together with your families.

“So it ended up being a great trip for us, not only as a life experience but bringing our team together. We ended up having a really good year that year.”

John Shea is The San Francisco Chronicle’s national baseball writer.