Back in 2017, 25.4% of all households in Japan tuned into just the first round games (albeit that's the only info I could find in like 2 mins of googling). Now Japan has Ohtani playing for them again, and his stardom has only grown after he dominated MLB in '21 and '22.

If they make the finals, I could see viewership in Japan being even higher than the world cup. Afterall they have their Koshien tournament, which is a high school baseball tournament, that is basically as big as March Madness is in the states.