score:6
There are a lot of rules for what you're can and can't bring on trains, but in my experience enforcement is very lax if you're not being an obvious nuisance β there are no conductors with tape measures inspecting every piece of luggage that comes in. So while your mileage may vary, I suspect you'll be just fine even though your yumi is 2.3m instead of 2.0m.
Here's a random forum thread (in Japanese) discussing bringing various awkward objects including a 2m-long sword (!) on Japanese trains and buses, and nobody reported any problems.
Upvote:3
You should have no trouble at all with a Yumi (longbow) on the trains in Japan. I see people carrying them all the time. I wouldn't worry about it.