There is a promotional video for March Comes in like a Lion (aka 3gatsu no Lion) called March Comes in like a Lion meets BUMP OF CHICKEN. It expands the closing song of the anime, Fighter, into a 6-minute music video, produced by the manga's author Chika Umino and the band BUMP OF CHICKEN.
I may have that backwards, though. The video may have pre-dated the anime by over a year, making the closing song a condensed version of the music video. From what I can gather, a DVD with the video accompanied special copies of the 10th volume of the manga, released 28 Nov 2014. The anime was announced 25 Sep 2015. If the music video pre-dated the anime, who animated it? Studio Shaft (producing the TV show) may not have even been involved.
add: The music video definitely predates the anime. It was posted to YouTube on 8 Dec 2014.
Much of the art in the music video looks like it may have come from the anime (and a lot does not), but that could just be that they both share the manga as source material. Also was the music video made in Flash? Parts of it have that mechanistic feel, but I do not know enough about Flash video capability to know if it would have been up to the task.
The [Show More] section of the YouTube video has a link to a Japanese site or page apparently dedicated to the music video: 3月のライオン meets BUMP OF CHICKEN｜白泉社. It is somehow protected and won't translate (not that a translation would be very accurate). I can't even drag over and copy text from it.