Well, first of all make sure that you are comfortable in front of his friends, and he is the same with yours.
Try not to have too many people around that will give you lots of attention, since this may make him feel uneasy.
Start a conversation! You could possibly start off by asking something like ' What is your next lesson? ' and think of things that link into this, beforehand.
Listen to some music before you see him. I'd personally listen to some music in the Rap Genre; since it makes some people less nervous and feel more invisible and incapable to do more things.
Find a reason to leave. Catch up with another friend? Gather together a group? Whatever. But when you are about to leave, give your friends a gently hug, allowing him to see that this is your way of saying goodbye.
Go ahead and don't be shy! Say bye to him, and give him a quick hug. But don't make it awkward. Relax, and make him feel secure.
Chat with our AI personalities