Jeremy is a teenager who feels lonely and doesn't have anyone he feels close to. He meets an alien bug from outer space who was sent here to form a symbiotic relationship with a human and become a superhero, but she doesn't want to because she's scared of humans (her planet doesn't really have a concept of "anger".) They have a meet-cute and then decide to fuse with each other when the bug is going to get attacked by some sort of superhero police.
The other kid is someone who also fused with a space bug but is acting much more destructive, and Jeremy and his space bug (they can mentally take over from each other at any time) start following this guy and trying to stop him from destroying stuff.

The bug can stay completely hidden when the human is in control. When the bug takes over, a full body suit forms around the human body, which is a form of magical armor giving them super strength, flight, invulnerability, cool yellow eyes, and the ability to breathe underwater (or rather, to survive without breathing.) When the bug is talking, it is in their own voice but using the human's mouth (they cannot talk in each other's voices.)