I think it’s related to extroverted who get depressed and engage with sexual activity as a way of self harming. And I think while it could be expressed as depression, this case specifically it rather more of a manifestation of PTSD trauma response, which came from playing as both the victim and the perpetrator in MC personal life story.
An underlying cause/PTSD could also be MC was forced to mature too quickly in pretence of a good son, good brother, good friend. Human seek love that evoke what they want, what they need, and what makes them feel familiar or safe. Human also have a hard time distinguishing their own feelings when emotions and situations get entangled. When you force a person to mature too quickly, and put them in an complicated circumstance, they get trapped, mentally suffocating, leading survival instincts taking over, including senses became dull, memories fading or blurred, repeated visits of traumatic memories, and seeking safety/ground-ness.
In a sense, it’s also why porn or sex is such a big thing in the human culture right now. Cause broken children’s tend seek something that can fix them, anything, love, gratification, euphoric sensation from drugs and sex, while not aware how it develops into an addiction, an escapism, an outlet. Cause education system focus on making u a cog of the society, but not a healthy functional human being that have a good sense of self, and a good relationship with sex or any sort of addiction/euphoria/escapism.
I think i was on the verge of a mental breakdown myself reading this. At least it wasn't long...the sex scenes are good but everything else? Eh....even as someone clinically diagnosed with depression, I couldn't make sense of a lot lol