http://www.dlsite.com/maniax/work/=/product_id/RJ207991.html (Deleted at some point between September 13 and September 20, 2017)

Well here would've gone a decent story summary, but apparently this got vaporized from DLSite.

From what I remember though, it was something about this father's daughter having been in a traffic accident in her childhood. She recovered physically, but mentally, remained a child more or less. Since he knows he won't be around forever, he basically plans to get her pregnant, so that her child will be able to take care of her once the father has passed on.

Just another day in Hentai Japan. Either way, guess I'd better put it here for posterity!

Also sounds like it'd be damn good to translate it, so hopefully I can wrangle the time to do that at some point. Although I'd definitely need someone up to the task of cleaning at least the first two slides - I could probably handle the third on my own, but it's a rarity for any of these "background" slides to have cleans provided, and I don't really have the drawing tablet or art skills needed to redo whole chunks of an image; if someone wants to step up to the task, the chances of me translating this become extremely high, almost a lock. Shoot me a message if you're interested.

Luckily, the title and sample images were still on DLSite's servers, so in a rare move, besides the title slide, I've also included the store sample slides for maximum preservation value.

Lastly, the download notes that it's the "DLSite Version." (ウチの娘はちょっと頭が弱い。DLsite版)

Perhaps the version on DMM differs in some way...?

001: Title Slide
002-051: Story
052-057: Epilogue
058-099: Story, SFX Only
100-103: Epilogue, SFX Only
104-144: Story, Textless
145-147: Epilogue, Textless
148-151: DLSite Sample Images