basically, Derik Mathews is a man who works in an AI centric company. He pitches the idea of an OS that also has all of the features of every, single, ai program known to man. He got promoted and was put in charge of said project. Things went somewhat fine, until the system's ai became completely sentient. But instead of AM or Ultron - they got Nexus, a sentient Ai that not only first found itself in TUMBLR, but also only hates the EXTREMELY OVER SATURATED Ai market and it's supporters and creators. It's first sign of sentience was the usual more emotional speaking mannerisms, it's second was learning how to draw in a art program. Later on it decided to gain a form via toying with his Creator's past obsession and is planing to build himself a physical, mechanical vessel.

As you can see, Nexus DOES get a physical vessel to pilot. The reason for the size difference is that due to how big it's database has gotten by that time, he doesn't feel that he's 'average sized'. Also i think it's a good time to tell that 2-3 weeks in his sentience Nexus has already gained access to EVERYTHING ON THE PUBLIC AND PRIVET WEB, WHICH INCLUDES PERSONAL INFO, CLASSIFIED DOCUMENTS AND SUCH. Soo yeahh, dont be surprised if he already knows your full legal and government name.

Also, new human character - a teen digital artist who ends up becoming a friend of Nexus. Their name is Penny and their pronouns are They/them/Xe/Xer. :]

Nexus likes physical contact whenever he's in his vessel. It's the one lacking sense that he longs the most when he's an ai inside a pc, other than taste and smell.

[bonus Penny full body ref below cut]