On January 19th, the Nikkei Shimbun reported the National Institute of Population and Social Security Research, in its announcement in December 2023, revealed that the estimated population for the year 2040 surpassed the estimated figures taken in 2013 in all eight prefectures of the Kanto (Greater Tokyo Area plus Tochigi and Ibaraki prefectures) as well as Yamanashi prefecture.
Notably, there is an upward revision in municipalities along the Tsukuba Express (TX) line which opened in 2005 to alleviate pressure on the JR Joban line which had then reached maximum capacity.
Once completed, the TX reduced the time needed to get from Akihabara to Tsukuba by half.

Courtesy of the Nikkei Shimbun translated by Patience Realty.
As of 2023, Tsukuba Mirai City in Ibaraki Prefecture has the fourth-highest growth rate among municipalities in the Tokyo metropolitan area, with a projected population increase of 51.4% compared to the year 2013.
The popularity of the city is attributed to the convenience of access to central Tokyo through the TX line, as well as the comparatively lower land prices than neighboring Tsukuba City, attracting young families seeking homes.
In response to the population growth estimate, Tsukuba Mirai City has initiated actions, commencing the construction of Child-Rearing Support Housing, consisting of two three-story buildings with a total of 57 units.
This marks the city's first construction of housing specifically focused on child-rearing.
Similarly, Saitama's Misato City along the TX line experienced an upward revision of 44.9%, reaching approximately 142,000 people in the year 2023 from the estimated 98,000 people in the year 2013.
Considering nearby Yashio City's 42.2% increase, it is inferred that TX line development significantly influences Misato City, similar to Tsukuba Mirai City and Chiba's Nagareyama City.
According to the Municipal Affairs Division of Misato City, industrial land development is progressing around Misato Interchange as part of the city's land readjustment project, potentially contributing to retaining residents.

Courtesy of the Nikkei Shimbun translated by Patience Realty.
In November 2023, the Misato-Nagareyama Bridge toll road opened between Saitama's Misato City and Chiba's Nagareyama City.
This is anticipated to address the increased traffic demand due to TX line development, potentially shortening travel times between eastern Saitama and eastern Katsushika in Chiba Prefecture.
Source:
Nikkei Shimbun (Japanese only; paywalled)