Liar-soft Fanclub Magazine "Gekkan Uso" (Monthly Lie)
Contrary to its name, this was a quarterly print publication issued by Liar-soft to its paid fanclub members.
As part of its run, the magazine had a multi-page advertisement for Kindred Spirits (available untranslated here), five issues of a Kindred Spirits illustration + Q&A column, one segment detailing the school's history, and an advertisement for the first drama CD, as well as a segment about the school cafeteria.
Additionally, Kindred Spirits characters were featured in some magazine illustrations (including a celebratory illustration for volume 50) and a 4-koma comic. Reports of a June 2019 fanclub mailing containing a 1koma featuring Sachi and Megumi also exist, but I'm unaware of any further details.
Gekkan Uso (Monthly Lie)
Kindred Spirits Content
BugBug Magazine
For some months after the game's release in 2012, Kindred Spirits' publisher, Liar-soft, ran multiple articles in the eroge advertisement magazine BugBug.
This included a corner introducing the game (untranslated, but including a short story that has been translated), a short colored manga, and a number of illustration columns.
As a precaution, do note that some of the art in these columns is quite suggestive.
BugBug Magazine
Kindred Spirits Content