Tonto is a male cat-like alien with brown fur and black eyes, serving as the third crew member aboard a three-cat invasion fleet from another planet alongside a captain and a fellow member named Sagan. Their mission is to travel to Earth and conquer it.

He displays a notable curiosity about Earth, specifically regarding its nature after their planned conquest, a trait that distinguishes him within the group. The cats' journey intersects with the human world through encounters with Juri Kibayashi, an occult-obsessed teacher they mistakenly identify as the "King of Cats."

While on Earth, the alien crew struggles to maintain focus on their mission as they become increasingly drawn to the planet's laid-back lifestyle. Tonto and his companions experience internal conflict between their original objective of planetary domination and the temptations of Earth's relaxed existence. The narrative explores their evolving perspectives and adjustments to terrestrial life as their invasion plans advance with limited success.

Tonto's origins are extraterrestrial and scientific, rooted in the "science of the Tuna Mayo planet" responsible for the crew's creation. Details regarding specific developmental arcs for Tonto across expanded media such as movies, OVAs, or spin-offs are not detailed.