Bic Camera is an electronic store from where you can buy a sim card. There are lots of choices and the staff is friendly.
NinetyTwo 13 by Tokyo Chapter offers great collaborative workspaces and living spaces centered around a community of creators. The workspaces range from hot desks, dedicated cubicles, customisable offices and soho apartments + all members have access to conference rooms, lounge, kitchen, showers, workshop and most importantly a commercial grade high speed wifi Internet.
Decently priced capsule hotel/hostel. Loved how clean and organized it was with a good WiFi. They also have a nice community area where you can work for a while. Although Ginza is a more peaceful and posh area of Tokyo and shuts early. If you're looking for a co-working space around check out Ginza Hub where you can find things in English.
Tokyo over New Years week is quiet and a lot of shops and restaurants are closed.
Impact HUB is a community for entrepreneurs creative and more. They will even let you organize events in their space. You can join as a member or just stop by for a coffee or special event.