Miri

About the character
 is Mars' half sister (as she is a robot created by Dr. Kawashimo who created Mars' electronic brain), and the deuteragionst in the series..

Miri, diferent from Mars, is more mature and responsible.

She has a huge respect for her creator to the point of accepting him as her father rather than just the man whom created her.

Miri also has a special ability which allows her to repair damaged objects, although it's not explained how she can do such a feat.

Story:
Dr. Kawashimo had created her when he was still making Mars' electronic brain and when he delivered it to Dr. Yamanoue, Miri was already fully operational.

Mars later takes an interest in Miri and then decide to visit her more often, to the dismay of his creator who is not quite in good terms with Dr. Kawashimo.

Miri is rather compassionate and kind and will always help those in need.

She acts like an older sister for Mars and usually has to deal with his childish nature.

Trivia:

 * The spelling of Miri's name in kanji is 美理. One of the meanings of 美 is beauty/beautiful and 理 can mean reason, logic, etc.