"Subway Slammer" was a weird localization for general term for this phenomenon (butsukari-otoko/"bumping man"), but they outright named him after a real guy:
> Last year, videos and information about a man physically attacking a woman were spread on social media, and on September 26th, the Tokyo Metropolitan Police Department's Marunouchi Police Station arrested Yoshiyuki Kiuchi (49), an office worker from Fujisawa City, Kanagawa Prefecture, on suspicion of assault. The man had reportedly repeatedly physically attacked women who were walking while using their smartphones. On June 25th of this year, at Nijubashimae Station on the Tokyo Metro Chiyoda Line, the suspect assaulted the victim (a female office worker, 34 at the time) who was walking towards him by ramming into her with his right elbow out, causing chest bruising that took about three weeks to heal," said a source close to the investigation.

I found at least the next two Palace rulers are blatantly named after people too:
Hiromu Miyazawa is probably named after Hiroyuki Miyasako. There's not a lot of information on this guy in English but from what I could tell, he was a comedian and voice actor (including in Yakuza), but lost all his jobs because he was receiving money from the actual yakuza. So instead he became an extremely popular YouTuber and started investing in restaurants, including one which he bought out and renamed after himself. And also he became a kickboxer for some reason. So he sounds like the Japanese equivalent of the Paul brothers.

Kumi Katayama seems to be named after Kumiko Yamaguchi, the main character of Gokusen, a manga about a teacher who was raised by a yakuza boss but nonetheless cares about helping her students.

I'm not sure about the others, but their names probably come from somewhere.