Two of my characters are 100% Mary Sues, that I gave a story and a background that helped them to grow. I gave them love interests that were fantasies of what I thought a lover should be. I don't care. It's not for them, It's for me. If someone else likes it, great, and if not, tough.
Handy guide to writing asexual characters < number ten is a good point for writing introverts as well- don't make your character introverted/asexual just so you can fix them it's boring, old,and aggravating most of the time.