Kato first worked for Tecmo on Captain Tsubasa and the original Ninja Gaiden trilogy for the nes, his time at Tecmo was from 1988 to 1991, he went under the pseudonyms of “Rummaru” and “Runmal”. He then went on to work for Gainax on the anime Nadia: The secret of Blue water in 1992, his last project at Gainax would be Princess Maker 2 in 1993. He then went to Square where he famously penned the script of Chrono Trigger (based on a story draft by Yuji Horii) as well as Radical Dreamers, parts of Final Fantasy VII, Xenogears and Chrono Cross.
Kato left Square after writing the plot of Final Fantasy XI: Rise of the Zilart to become a freelance scenario writer. In addition to games for different companies, he has continued to work on Square Enix projects such as the World of Mana series.
It was announced on September 21, 2011 on the official Team NINJA twitter account that Kato would be returning to the Ninja Gaiden series with Ninja Gaiden 3 for the Xbox 360, PlayStation 3 and Wii U to write the script.