"Don't you have anything... you want to protect?"
—Epsilon to Pluto

Epsilon is a Kokoro robot (the only one clearly shown to be female) that moniters Metro City's weather and marine wildlife. She uses light as her source of power (shown in the manga).

Ever since she was introduced in The Rise of Pluto, she has been a recurring character ever since, sometimes even taking on the role of Astro's bigger sister (again, clearly shown in the manga where she hugs him). She, too, shares Astro's belief that humans and robots may one day live as one, and (like Astro) has often tried to make it a reality.

She is a nominee for the Robot of the Year Award.

She is hinted to the the sister of Delta.



Epsilon is shown to be nice, gentle and caring, however when duty calls she still can bravely fight (alongside Astro). She has a bond with all the marine animals in Metro City, which she cares for, and when she fought Pluto she tried to keep the dolphins out of harm's way.

Role in "The Rise of Pluto" and "The Fall of Acheron"

In The Rise of Pluto and The Fall of Acheron, Epsilon is shown to be one of the "World's Strongest Robots" that Pluto challenges. Shown to be by far the post successfull except for Astro (that she almost destroyes Pluto) she was foiled by a pod of dolphins which were swimming nearby. Epsilon urgently told the dolphins to "stay away", forgetting about Pluto, which Pluto labells as her "weakness". Pluto responds by swimming near a highly volatile area of the ocean, if Epsilon shoots; thousands of marine creatures will be killed. Epsilon refuses, and Pluto afterwards successfully triumphs over her. Interestingly enough, Pluto decided not to destroy her (like he destroyed Hercules).

Role in "Escape from Volcano Island"

She was again featured in Escape from Volcano Island, where she was a nominee for the prestegious Robot of the Year Award (presented by Dr O'Shay) on board the "Carmela Queen". Unfortunately, the ceremony was interrupted by Mr. Drake, who steers the ship's path straight into a volcano. Epsilon the again helped Astro, this time to stop the rocks from crashing the ship. Due to her bravery and courage, she was pronounced one of the winners of the 2043 Robot of the Year Award.

Role in the Robotonia Episodes

Epsilon once again received a significant role, this time in the Robotonia episodes. After Reno and Hannah crashed Yuko's car, Epsilon helped them to their goal by steering the car herself while managing to avoid the lasers of of humans. Reno, afterwards, was extremely grateful to her.

Other appearances

Epsilon was given a brief cameo when she appeared after Astro was being rebuilt following the incident in Robotonia.


Epsilon know for her abilities of to which Astro doesn't possess.

  • Weather Manipulation: Epsilon's most notable ability is the manipulation of the weather. She uses this to stop a tornado in the episode The Rise of Pluto.
  • Marine Communication: Epsilon is also able to commune with the marine wildlife.
  • Water Current Detection: Epsilon can also detect ocean currents.


  • Astro Boy: Epsilon acts as a older sister to Astro, as she hugged him in the manga.
  • Delta (Possibly): It is hinted that Epsilon is the sister of Delta.