The hotel communicated with me via email that we could stay in any room based on our kids' ages. I think I shared this upthread a bit, but maybe it was in a different Tokyo hotel thread.

Overall I found that the majority of Tokyo hotels were very accommodating to our family's 4 pax configuration beyond what the website shows...maybe there was just one property that said no. Contrast this to London where it is almost precisely as the website shows, or maybe it is indeed precisely. Iirc there wasn't a single London property that said they would accommodate beyond what the website shows.