This is an office building but the ground floor is usually open for public. Inside the building, there is a small lobby area where there are seats and plugs under the benches on the wall. Also, if you go outside, there are standing "desks" with power sockets as well. There is a Kanda Square public WiFi which is not the fastest but usually gets the job done. If you need any drinks or food, the building has a Lawson, Summit (supermarket), and Tully's + a few more dine-in restaurants. I see the lounge area in the picture is quite popular and seats are almost full by 10AM.

I think the building itself is open 24 hours but not sure if they allow work in the lobby late at night. I've exited entered the building quite late at night though. Outside plug is definitely open 24/7 🤣 Bathroom is definitely super clean, and there's a smoking room on the ground floor if you need one 🚬