After Aizen won the war, Chad had some decisions to make. He wanted to help out, but he wasn't a shinigami and didn't want to die to become one; additionally, he still wasn't at the level of strength he'd need to make a difference. So after the battle in the King's Realm, as things settled into a sort of shellshocked routine in Soul Society, Chad went traveling. He flew to Mexico and has spent the last two years exploring his ancestry, figuring out who he is and who he wants to be, and pushing himself to fully understand his powers by fighting against bad spirits. From time to time he would send Ichigo postcards (via Isshin) and even more occasionally got one in return, but it's been a largely solitary journey, marked by the short-term passage of people in and our of his life.
Now, over a year later, he feels stronger and able to make better use of the abilities he has, even if they're not on the same level of others' in terms of raw strength. He's not sure he'll do, but he'll start by returning to Karakura.