So let's see what Kurumada had to say one last time, as well as how a veritable hall of fame of manga legends (for the most part, at least) felt about the man himself back in the early 1980s!
Volume 19 of Ring ni Kakero came out on November 15, 1981, roughly a month after the final chapter, the first one in Jump history to be published entirely in color (in this case, full color opening pages & red-toned pages for the rest), and it's the only tankouban to see release during the interim between RnK's finale & the debut of Fuma no Kojirou a few months later. Also, as you can see to the left, around this point Shueisha started including what looked like a proof of purchase of some sort in the bottom left of a tankouban's dust cover's inner front flap, next to the author's note, featuring the blue outline of an apple with "LOVE" written on the inside (*cue Haddaway*). For this volume's author's note we see Kurumada describe life itself as being like that of a poem, and that one should aspire to live their life as though it was poetry:
"For men, their life itself is a poem.
Poetry is an aspiration. When the anger, joy, sadness, and passion of the heart are embodied in our actions, without embellishment or pretense, it will surpass any great poem in the world.
I hope to write good poems that will touch your hearts and convince you."
Volume 19's afterword comes from Yoshihiro Takahashi, best known today as the creator of various dog-related action/drama manga, most notably the Ginga Series (Ginga - Nagareboshi Gin, Ginga Legend Weed, etc.). However, back in late 1981 Takahashi was still two years away from debuting Gin, though his OG dog manga, Shiroi Senshi Yamato, was still running in Monthly Shonen Jump. Instead, by this point he had completed his first hit manga, baseball series Akutare Giants, the year prior & was about 16 or so chapters into his next Weekly Jump series, the fishing manga Aozora Fishing, which he drew for writer Hiroichi Fuse; sadly, this series would end in mid-1982 after only 42 weekly chapters across five volumes. For this afterword Takahashi looks back on when he risked missing the deadline for the very first chapter of either Akutare Giants or Yamato, as they both debuted in the same year & Takahashi just says his "first serialized manga", so his editor sent over some scrappy little artist to assist him so that he wouldn't be late: Masami Kurumada. This would likely be in early 1976, after Sukeban Arashi's cancellation in late 1975, but before Ring ni Kakero's debut in early 1977 (& also before Kurumada's one-shot Mikeneko Rock, which appeared in Monthly Jump at the end of 1976), and is the only proof I've ever seen of Kurumada being an "assistant" to Takahashi, though it seems to have only been for a single chapter: