Are Chinese and Korean media outlets spying Japanese media since they share the same office address? No, that's not true: Many foreign media have local news bureaus in buildings where Japanese media are based and there's nothing secret or furtive about that.
The claim appeared on a TikTok video (archived here) on April, 13, 2023.
The text on the video, translated from Japanese by Lead Stories staff, reads:
Are they manipulating our information?
This is what the post looked like on TikTok at the time of writing:
(Source: TikTok screenshot taken on Tue May 23 12:33:51 2023 UTC)
The fact that different media share the same address does not mean that they are spying each other: It is not uncommon for foreign media to share offices or work spaces with other locally-based news organizations.
Korean Broadcasting Corporation (KBS) has a branch office inside Japan Broadcasting Corporation (NHK). In 2005, TV Asahi showed a documentary about the daily life of the KBS Korea crew members. It explained:
Korea Broadcasting Corporation KBS Tokyo branch has an office in NHK. Yang Ziu, a correspondent who came to Japan last July, goes to work at 4:00 in the morning. He reads all the morning papers, he summarizes the main news and sends a report to the head office in Korea. Then, upon receiving a request from the head office, the interview begins. The KBS Tokyo branch, which opened in 1974, has a total of 13 staff, including 10 Korean staff and 3 Japanese staff. It can be said that the scale is quite large compared to the branches of other foreign broadcasting stations.
It then added the major news delivered by KBS Tokyo bureau in 2005:
(1) General election: Liberal Democratic Party's overwhelming victory
(2) Shimane Prefecture's Ordinance Concerning Takeshima
(3) Junior high school history textbook problem
(4) Japan becoming a permanent member of the UN Security Council
(5) The issue of Japanese abduction by North Korea: Megumi Yokota's remains were fake.
Nippon Television has a business partnership with South Korea's Seoul Broadcasting System (SBS) as clarified when the first joint TV show production between Nippon Television and South Korea's SBS was announced on December, 28, 2000.
The Asahi Shimbun newspaper has a partnership with the Korean newspaper Toa Nippo. On the Asahi Shimbun Globe website, Toa Nippo (Korea) is introduced as follows: "One of Korea's leading newspapers. First published in 1920. The head office is located in Seoul. New Toa, Women's Toa, Weekly Toa, and Science Toa are also published. It has also a comprehensive TV station, 'Channel A', as an affiliate. In Japan, it has a partnership with the Asahi Shimbun."
The CCTV (China Central Television) website states that in 2008 CCTV attended a ceremony to inaugurate a partnership between China International Television Corporation and NHK.
As to NHK, it has cooperation agreements, and exchange of news material agreements with over 40 countries.