@notjustbikes Oh your awkwardness gets worse I'm afraid! 😄
It's the only train in the Tokyo area where you can take your bike on board as-is. All other trains require using Japan-unique bike bags, which involve removing both wheels and wrapping the bike completely, then carrying it as luggage. I did it for years and to put it mildly, it's a pain!
You could have done this trip on the Wakashio limited express, but that isn't one of JR East's "joyful trains." 🙂
@notjustbikes I'm also surprised you went out of your way to book BBBase!
Unless it's changed since 3 years ago, it must be purchased through JR's travel system. Only available online (in Japanese) or at staffed "green window" locations at major hubs.
You typically select a recommended bike route and are then given the BBBase tickets that match it.
The BBBase is further only available in late spring and early fall on weekends and some holidays.