Change in behaviour. Why?

I know this guy for the last 2 years, and we are very good friends, and for the last couple of months he has been behaving different. He became very touchy, always teasing me and everyday when we say goodbye he gives me long tight hugs with neck kisses.

He has now started hugging me from behind, resting his head on my shoulder and kissing my neck.

He only behaves like this when we are alone.

He has a girlfriend, so I don't he has fellings for me. So why would he start behaving like this?

Change in behaviour. Why?
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