|Name in Japanese||猿飛 秀吉|
|Rōmaji Translation||Sarutobi Hideyoshi|
|Voice Actor (Japanese)||Masashi Yabe|
|Voice Actor (English)||Anthony Bowling|
Hideyoshi Sarutobi (猿飛 秀吉, Sarutobi Hideyoshi), often referred to as Saru (or Chimp in the English dub), is a friend of Nagasumi who is often portrayed as a perverted monkey (a pun on his name; "saru" meaning monkey). He later became Kai's "servant" and always protects and helps him when he is in need. In the beginning, Saru's reasons for befriending Kai are because of his fortune; however, in episode 24 it is shown Saru genuinely cares for Kai. His name is related to Sarutobi Sasuke and Toyotomi Hideyoshi (Who himself was also often called "Saru/Monkey"). A running gag between the two, in line with Saru's name would be him acting like a ninja for his master(Kai). Saru occasionally appears dressed as an old hermit, "ero-sennin" (erotic/perverted thousand-year-old), who periodically appears to offer insights of perverted sagacity, When in the old hermit form he calls himself "Saru Roshi" a parody of Master Roshi from Dragon Ball.