Eyy, some people feel so useless they thought it's better for them to disappear.
MC probably thought the same. He need a place where he's needed.
It's human's nature.
The MC has a traumatic experience since he's a child remember when he lost his family and he thinks that it was all his fault that made him overthinks that he'd carry a bad luck so when he woke up he probably don't wants his aunt to get involved with his unfortunate.
That's why he made a choice to stay in that gang
His aunt is probably even more stressed since he’s missing again. She searched for him for over half a year and now he’s been kidnapped right after she found him and he doesn’t even want to go back