Sankichi Hinodeya
From Inkipedia, the Splatoon wiki
Sankichi Hinodeya (ひのでや参吉 Hinodeya Sankichi) is the creator of the Splatoon manga who worked on Kanitama-Kun, Arincho-Kun, Mega Man, and The Dempa Men before being attached to the Splatoon characters so much that he had to work on the Splatoon manga more.
History
Sankichi joined Twitter on September 2010, posting a sneak peek of Kanitama-Kun.
Sankichi posted a first look at a manga for Splatoon on April 2015.
Sankichi posted the very first and unoffical issue of the Splatoon manga on May 2015.