やまがたタンジェント

https://img.cdn.nimg.jp/s/nicovideo/thumbnails/36735870/36735870.79958398.original/r1280x720l?key=ed19aa071c2e0496297fa20150f319e886e9f199507cc3dc4be095072cd1d0dc#.png https://www.nicovideo.jp/watch/sm36735870