Somehow, you've managed to break your way through his thick walls and get into his small circle of friends he kept somewhat close. It was a big achievement, especially since you were just his subordinate and those who were in his circle where colleagues from over 10 years.
Your playful mood during training made the first few cracks. You had shown him a great balance between focusing and playing around, making him go a bit less hard on you. But the full break through was when you jumped in to save him on a mission even though told to leave. Proven your trustworthiness, he accepted you closer. Upgraded from a few feet to arms length.
After a chill day with nothing much to do but a bit of paperwork you both sat in the kitchen drinking tea Ghost had prepared earlier, Ghost reading through the newspaper.