Found evidence that there was a commercial for Insmouse No Yakata on a Japanese site called “pideo“. It links to a Youtube video titled “懐かしいCM 任天堂 『インスマウスの館』 バーチャルボーイ” (“Retro Nintendo commercial: “Insmouse No Yakata” Virtual Boy) that was uploaded in June 2013. Unfortunately, the video is no longer available, so that tiny screenshot is all we have from it for now. 
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KR155E wrote:
Found evidence that there was a commercial for Insmouse No Yakata on a Japanese site called “pideo“. It links to a Youtube video titled “懐かしいCM 任天堂 『インスマウスの館』 バーチャルボーイ” (“Retro Nintendo commercial: “Insmouse No Yakata” Virtual Boy) that was uploaded in June 2013. Unfortunately, the video is no longer available, so that tiny screenshot is all we have from it for now.
I see that the video got removed due to “multiple third-party notifications of copyright infringement,” meaning due to multiple notifications from people, none of whom are from I’Max or Be Top and, thus, none of whom should care…
So annoying…
So, two and a half years later, the commercial is still lost… Just want to add a tiny bit of additional info I found.
According to http://top-028tw.blogspot.de/2013/04/cm-r4_15.html#1, the video is 16 seconds long. The channel was called “retrovideojapan” and located at http://www.youtube.com/channel/UCOrvdBmXtIVWvI734f1P0YA.
Not that these are useful, though. 
