This building is mainly Chiyoda city office but the 9th and 10th floor are public library where anybody can access for free. On the same floor, there is a food court with great view and lots of food options for a reasonable price. The library area has a lot of individual booth but they are technically limited to those who have the library card, which is not too hard to get at the reception. There are also free address tables. There is unfortunately no places to take any calls. WiFi speed really depends on the location. Some part of the library struggled to get signal, but other parts had 20 to 30 Mbps download. On the ground floor of the building, there are a few seats available for everyone and Chiyoda city WiFi is quite reliable down there. There is a bakery and a coffee shop there so not going up to the library is also an option.