空が灰色だから
A 2011~2013 omnibus manga series by [[Abe Tomomi]], serialized in akita Shoten's "Weekly Shounen Champion.":http://en.wikipedia.org/wiki/Weekly_Sh%C5%8Dnen_Champion

h4.See also

* "Wikipedia article (JP)":https://ja.wikipedia.org/wiki/%E7%A9%BA%E3%81%8C%E7%81%B0%E8%89%B2%E3%81%A0%E3%81%8B%E3%82%89
sora ga haiiro dakara