Zeno has just begun his great investigation of the current state of the corps.
He is lying flat on his stomach observing the aftermath of the hashira meeting that just happened from the roof of the house. It gave a clear view on what is happening on the engawa of the house opposite to him.
Kuroshi Junpei is a weird man, Zeno decided. The man was the currently oldest hashira of the demons slayers at age 46, surviving to this age with the lethality of the wind style. The most experienced, the strongest, the one people of the corps thought of when they think ultimate strength they can reach as humans.
Junpei was considering retirement. Considering because the mission Kareki suggested to him had such an increased chance of encountering an upper moon, aka certain death for the wind hashira. Because Junpei had aged so much was the biggest reason why Junpei wouldn't survive an encounter with an upper moon. Zeno could get that much out of Junpei's conversation with the current Flame hashira Rengoku Eijuro.
Eijuro would be considered the oldest if Junpei retired and he was resigning himself to shoulder the kind of pressure and responsibility being the oldest came with.
Eijuro, Zeno could clearly see was a descendant of the flame pillar, Kajiri Takeo, from when Kameki was the head. Even before Takeo, their family had very distinct looks and had been prominent in the corps so it was no surprise the line was still staying strong.
He thought he recognized a few names from the conversation, like the name of Eijuro's recently born son, Rengoku Shinjuro. That was a character still alive in the original story. Zeno also recognized the current young water hashira. Urokodaki Sakonji happened to be a very important person to the story.
He then heard the name of the new rather young, some 18-ish year old, lightning hashira, and couldn't recognize the family name. He had almost frozen when he did not in fact recognize the name, he really slept for a far longer time than he was supposed have.
He had wondered where his brother's and sister's descendants were. He promised to protect them. Tracking them down after a small nap of a few decades would have been child's play. Now it's been 2 centuries and he doesn't know for sure if he can track down Hinoe's or Zeuxis's descendants.
He could only hope the Ryumaki blood ran strongly and their families kept producing lighting hashira's. So, investigating one Kuwajima Jigoro's family line would be added to his to do later list.