Join Date: Aug 2011
Location: Barcelona, London, on a plane
Programs: IB+ Gold, TK E+, Hyatt Globalist, Marriott LTP, IHG Diamond
Posts: 14,182
Japan is very strict. Book for 1 and show up with a guest... you have an issue.
There certainly might be rooms that can accomodate 5, but you might find it more cost effective to book 2 rooms. Depending on children's age of course...