Saiki Kusuo no Sai Nan Wikia
Saiki Kusuo no Sai Nan Wikia
Saiki Kusuke
Character Name
Full Name Saiki Kusuke
Kanji 斉木 空助
Furigana さいき くうすけ
  • Dr. Kusuke
  • Ku-kun (By Kurumi)
  • Big Ku (By Kurumi (English dub))
Personal Info
Epithet Genius
Age 19 years old
Birthday June 16
Sign ♊ (Gemini)
Blood type B
Gender Male
Height 179 cm
Weight 63 kg
Occupation Inventor
School University of Cambridge
  • Graduate (PhD)[1]
  • Post-graduate[2]
Manga Debut Chapter 94 (Cameo)

Chapter 103 (Debut)

Anime Debut Season 1 Episode 19 (Cameo)

Season 1 Episode 21 (Debut)

English Voice Chris Patton
Japanese Voice Nojima Kenji

Kusuke Saiki (斉木 空助, さいき くうすけ lit. Saiki Kūsuke) is Kusuo's older brother, a super genius who likes to invent machines/devices. He is 2 years older than Kusuo.


Chara Kusuke.png

Kusuke, like Kusuo, was born with a different hair color than his parents. He has blonde hair and slightly darker eyes. He wears his "Telepathy Canceler" whenever he is around Kusuo. When working, he is mostly seen with his machines, wearing a typical white lab coat worn by scientists. When in school, he wears a long black robe with a white collar buttoned up, and while on his days off, he wears normal clothes such as a t-shirt and pants.


Kusuke ahyu.png

Kusuke is prideful and competitive when it comes to Kusuo. He would have done anything to win against him when they were kids. However, he would always lose against his little brother. Thus, he became addicted to playing/fighting with Kusuo. Kusuke is a sadist, as shown when he enjoyed seeing Kusuo, Shun and Riki being chased by crowds of people. Kusuke is also obsessed with Kusuo and can be attention seeking and selfish. This is best shown when he made a time machine to go back 20 years in the past when Kusuo was still alive (in this chapter, they were in a parallel universe where Kusuo had died[3]) and when he made Kokomi cry by saying that she and Kusuo were not fit for each other.

He is also deceitful, always showing an angelic smile towards their parents. He ignores his father, just like Kusuo. Kusuo always thought that Kusuke hated him, but Kusuke cleared this up and told Kusuo that he only liked to tease him.


Kusuke was born on June 16th and was raised by Saiki Kurumi and Saiki Kuniharu. At 1 month old, he spoke his first words and quickly was able to communicate with his parents. He then was able to write and do math at the age of 2. Not long afterwards, his younger brother, Saiki Kusuo, was born. Kusuke always competed against his younger brother and lose every single time.

Sometime in middle school, he, along with Kusuo, created the control devices that Kusuo wears.[4] At the age of 14, he leaves to England and studied in Cambridge,[5] getting a masters and PhD.[6]


  • Like the rest his family, Kusuke's name is a pun on the word Psychics (サイキックス Saikikkusu).
    • "suke" is common in Japanese given names for males.
  • He, along with Kusuo, created the control devices that Kusuo wears.
  • He has an IQ of 218.[7]
  • Similar to his brother, he is immune to Kokomi's beauty.


  1. Saiki Kusuo no Psi-nan Chapter 105
  2. Saiki Kusuo no Psi-nan Chapter 160
  3. Saiki Kusuo no Psi-nan Chapter 126
  4. Saiki Kusuo no Psi-nan Chapter 103
  5. Saiki Kusuo no Psi-nan Chapter 104
  6. Saiki Kusuo no Psi-nan Chapter 105
  7. Saiki Kusuo no Psi-nan Chapter 104


v · e Saiki Family
Members: Saiki Kumi · Saiki Kumagorou · Saiki Kurumi · Saiki Kuniharu · Saiki Kusuke · Saiki Kusuo
Miscellaneous: Anpu · Pushi · Warp