If you make a character that is antagonistic, antisocial, and decides to wander off away from the rest of the group to solo adventures, the DM is entirely within their rights to go "Congratulations, you're an NPC now. Now either make a character that will be a part of the group, or find another table" rather than running a separate solo adventure for you while the rest of the group sits around doing nothing. This applies equally to "I'm going to sail away to a new continent without the rest of the group," "I'm going to retire from adventuring to start a quaint little B&B," or any other form of choosing not to participate.