I've been looking for an animated series that I saw on a TV about 10 years ago. Here is what I remember about it:
- the main character is a teenager
- he is carrying some kind of robot which is very important and will help him save humanity. The robot looks like a mace and it can be plugged into ports on old hardware and significantly improve its performance.
- I also remember that closer to the end of the series there were a mech where this robot was inserted, so it looked like the robot become a head of this thing.
- people (part of them) are afraid of the sunlight, but they aren't vampires.
- those who are afraid of the sunlight are leaving underground.