池袋劇場酒店

Certainly it is too small for 2 people stay in a single room. It has only 12m to 14m. Also, the single room is only allowed for one person.
Double room has two beds and the size of it is 18m to 22m.
At last, I also agree with Chi's recommendation that you may consider to choose a semi-double room. It is cheaper and smaller with 16.5m to 18m and one 4-feet bed.
You can go to the following websites to have a look:
http://www.theatres.co.jp/hotel/guestroom/index.html#massage
http://www.kktravel.com/tyo/hotel/theatre/theatre.htm

I want to say even semi-double room is also small for two persons.

I went to 池袋劇場酒店 several month ago.

semi-double bed is just fit for two thin person.

If u a fat person ....u will feel the bed size is not enough!

However, the room space is enough to place 2 or 3 luggages.

Almost all Tokyo hotel is very small . I think go to sight seeing is Okay

although hotel is not big.

It was because u will go out early and come back to hotel at night.

if you want to save money, just take the semi-double one
It is fine if you are couples or 2 girls.
if you want to enjoy your holiday, you should take the double or twin room.