There is another series called Motto, Ikitai... Install published the same year and written by the same author although the artist is different, does anyone know what it is? A sequel, a spinoff, something else?
I had to look this up, lol.
My initial guess was that it was just another version of the same story but drawn by someone else. It's not really uncommon to happen, for example, the Psychic Detective Yakumo novel series had two manga adaptations (one was made years after the first serialization ended, yet got new material from the novels), but I think a much more recent example is The Apothecary Diaries, which has two simultaneous manga adaptations serialized by two different publishers.
So, yeah. Looking at both of their respective MangaUpdates pages, one was adapted with a shoujo demography on mind (this one, published in THE Margaret) and Install was for a seinen demography (Weekly Young Jump), in 2005. Unfortunately, I guess "Install" is the lesser known adaptation of the two, since there's almost no info about it online, besides Google throwing me shop links with very basic description from the first volume.
But, I was curious on "why" this was like this... and I had to dig deeper.
Turns out that Yoshi (the author) is actually a big deal in Japan. I went to his website and, his website's profile states that he is a famous writer (an all around artist, as it says that "he is not just a book author!) that is considered a "pioneer on mobile web novels/content", and "I Want to Live On" (Motto, Ikitai...) actually was a (famous) web novel of his. So, I imagine it was one of those cases that he made a deal with Shueisha to have his work adapted in two manga serializations (drawn by newcomers Yuki Ando and Masato Naka) for two different demographies, simulataneously (or very close to "simultaneous").