I live in Japan (and have spent 13 years of my life here) so I can probably offer some tips.
Viewing games live here is a great experience, but quite different from the US.
If you want the "full" Japanese experience, my recommendation would be to get seats in the right field bleacher seats. These are where the home team`s supporter`s club (
Ouendan) sit. Sitting with them is an experience nothing like in the US. You are surrounded by the most intense baseball fans in the world, with volunteers waving gigantic flags, playing instruments and engaging in organized cheering throughout the game. They are some colorful characters out there, half of them look like they are members of the Yakuza, but if you are a baseball fan willing to root for the home team then you are welcome.
This is what it looks like, though the video doesn`t do it justice
https://www.youtube.com/watch?v=k9qnhtcJ8C4
If you are the type who just wants to sit and quietly watch the game, then the infield seats are for you, but I do recommend trying right field sometimes (if you are rooting for the visiting team, the left field bleacher seats are reserved for their supporters club).
The best stadium by far to watch a game is Koshien, home of the Hanshin Tigers (located in the suburbs between Osaka and Kobe). Its a pre-war stadium that has been recently renovated, but maintains all of its old-school charm. It still has the all-dirt infield that all Japanese stadiums used to have. Jingu Stadium in Tokyo (home of the Yakult Swallows) is the only other stadium of historical interest still in use, and it is also worth checking out but isn`t as nice as Koshien.
If you are a traditionalist like me, one downside of watching games elsewhere is that half of the teams play in ugly domes (Giants, Dragons, Hawks, Lions, Fighters) which....I just hate. Stadium construction is just now catching up to the US trend from the 90s of retro ballparks, Hiroshima just opened the first such stadium in Japan and it looks like a nice place to see the Carp play (I`ve never been to a game there, but have seen it from the window of bullet trains as I pass through the city sometimes).