Of all the important things Shogo can bring to the Reds on and off the field, #1 on the list has to be his walk up song selection. There is a ton of Japanese music out there. For instance, he's got all of J-pop to choose from. That would seem the most obvious direction to go, but I know next to nothing about J-pop, so I'll leave it to others to make suggestions.
However he could go classic. Pick a genre from any point in the and the Japanese have acts in it. For instance, Japanese surf music. Yes, it exists. In fact, there's a lot of it and surf chords creep into a lot of Japanese rock and pop songs. Shonen Knife, the Japanese all-girl trio answer to the Ramones, were heavily surf influenced. And any Shonen Knife would be a great selection, though maybe Shogo wants to go with less of a throwback. So, here's three suggestions:
BABYMETAL will break you brain. Seriously, try to process everything that's going on with that band. And if you pick a BABYMETAL song, you pick "Gimme Chocolate".
Then there's anime, which it a huge deal in Japan (and has a cult following here). Theme songs from anime shows get heavy rotation in Japan. So perhaps something like "Uncrowned Greatest Hero" from One Punch Man.
Though, a walk up song is essentially entrance music. So he could lift pro wrestler entrance song, and if you're going to do that, might as well go with Tanahashi.