Here it is, the completely out of date but still useful visual guide to Kajishima's Doujin work.
Hopefully this website's section on the doujin will supersede its use, but it's still a neato picture.
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The Kajishimaverse has about different 5 primary uses for the various Doujins in it's cannon.
Some are used for introductions of concepts. such as the plans for Photon and Dual and his other shows.
Some are Original Storyboard dumps for comparison to the final project.
(To see what got cut and changed)
Some are little side stories that enhance the work.
Some are Spoiler pictures.
and some are explanations of things which got messed up by executive meddling
For more info on the Doujinshi's of Masaki Kajishima Click Here
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Here you can visually see the various groupings of the doujins which is nice:
1.The Chousen Ame series which he contributed a few pages to.
2. The few miscellaneous Doujins he contributed a few pages too.
3. The Notan Series: basicly storyboard dumps with lots of omakes, These things are rare and huge.
All the covers are spoilers for things which didn't come out until years later and it shows just how long ago the entirety of this series was planned.
(These are from around 1993-1996 and showcase the concepts for ova 3 and the true tenchi novels... and more if you believe my theory)
4. Kajishima onsen: The night before the carnival, the main doujin series featuring concept introductions, unfinished content, backstory, and short vignettes.
5. Kamidake onsen, Originally just a few of his drawings some are spoilers to things as far as 2017 (and beyond if you believe my other theory) later they tended to be storyboards and concept art.
Not pictured -IF-: which is storyboards for OVA 4, His vision for AI Tenchi that got passed on (Tenchi's kid's), and his vision for yet another show.