The Tokyo Yakult Swallows’ Tetsuto Yamada has been full of surprises since earning the Central League club’s regular second base job a year ago, and his home run in the second game of the All-Star Series last Saturday shows we never quite know what to expect from him.

The Kansai native made a reputation for himself as a slugging shortstop for Osaka’s Riseisha High School in the finals of the summer national high school championships at Koshien Stadium. Yet the park had not been a favorite of his as a pro — something that may have changed on Saturday. Three days after his 22nd birthday, Yamada took Tohoku Rakuten Golden Eagles right-hander Takahiro Norimoto out to straight-away left field.

“Playing an All-Star game there was great, but I have not done well at Koshien,” Yamada told Kyodo News on Tuesday at Jingu Stadium. “I haven’t been able to picture myself hitting there.”

Yamada is 6-for-27 in his pro career at the storied ballpark, not counting the double and home run the first-time All Star hit in four at-bats there on Saturday.

Since turning pro after the Swallows made him their No. 1 pick in the 2010 draft, Yamada has hit just five home runs in 712 minor league at-bats. But this year, he has 15 homers in a little more than half a CL season and leads the league with 29 doubles.

“The lack of home runs (in my first year) didn’t surprise me at all. That is the kind of batter I always was,” he said. “Even now, that’s not what I’m about.”

That being said, his home run on Saturday was different.

“I was actually aiming to hit a home run in that situation,” he said. “That was the only time I’ve done that, and I hit it really well. That was cool. It’s something you can’t do very often, but you can do things like that in the All-Star game.

“As far as doing something different to increase my power this year, that’s not happening. I did change where I hold my bat in my stance, and that’s helped me make contact lower on the ball, and my timing is better, too.”

After hitting .259 with few walks in the hitter-friendly Eastern League in his first season out of high school, Yamada changed the way he timed pitches for the 2012 season.

“When a batter first turns pro, he comes face to face with all those breaking pitches: the forkballs, the sliders and so on. That can really mess up your game,” Swallows batting coach Mitsuru Manaka said.

From his second season, Yamada adopted Japan’s nearly ubiquitous one-legged stance, and now picks up his front foot and holds it before planting and shifting his weight into the pitch. He quickly began hitting for average and walking more than he struck out. This year Yamada became the youngest interleague batting champion, when he posted a .378 average against the Pacific League and was batting .332 through Tuesday as the Swallows’ leadoff man.

“He’s become used to different pitches, and is much more selective about which ones he wants to go after in the zone, and then puts good swings on them,” Manaka said.

“He has great bat speed, and although he’s very slim, he’s actually quite strong. Those two things working together are going to produce some power.”

Although he’s not yet a Golden Glove candidate in a league where the Hiroshima Carp’s Ryosuke Kikuchi appears to have that locked up, Yamada is making strides on turning the double play as he makes the transition from shortstop to second base.

Even so, Yamada said he knows his bat is going to be his calling card.

“Fielding is important,” he said. “But batting is where I’m going to make it in this game.”