That super powerful alien (that Mori has the mark of on his cape) or one of its close underlings fell in love and somehow had a child with a human. Something happened to the human partner so after they found Mori in that basement they decided a human orphanage would be better for him to grow up in since he's more human-like than alien. But when he disappeared they obvi went looking for him. I think the one we saw recently wasn't the parent though, just works for the parent.
I have a bad feeling the human parent might be dead. If that's the case, I hope Rider becomes Mori's other adoptive parent.
I saw someone else recommend this in a comment on the reddit page, thought I'd pass it on. I'm using Google Keep for my reading lists now. I just "copy image" of the manga thumbnail art from here, then paste in new note on Keep to start an entry. Then it's an easy copy/paste for title, author, status, summary, etc. It lets you color code your notes too (I do mine based on main genre) and add tags/labels. It's nice that it's also automatically saved since it's browser based and opens up under my google account.
I want her name to have characters from both Kwon's and Ho's names since they're her dada and papa (╥﹏╥ )