Guy's Behavior

Why would a guy avoid eye contact with the girl he is interested in?

This year there's this guy in my bus who glanced at me often so I first looked back without thinking about it. Once a friend of him saw me looking at him from behind and the guy quickly glanced smiling to himself. The next day, I walked past him twice and he smiled at me, staring with shiny eyes and when I passed him and his friends he talked and they all look at me suddenly. I didn't smile back and the last time I saw him he had a serious face but two days later, we went out classes in front of each other at the same time as he looked at me, I smiled, he held eye contact, looked away and looked back. I heard his friend asking 'it s her?' and they stayed facing us from afar during break, talking.

The day after I smiled, he entered the bus, gave me a little smile and kept glancing on the side (I was on the side behind), seemed to listen to what I said. Since, he doesn't make eye contact except by chance.

I was once walking in front of him and friends and noticed from the corner of eye he was looking at me. Once I entered the bus, him and his friends were there and they glanced at me, but he looked down at his phone. When I stood up to let the girl next to me go, he (by chance his seat was next to mine, just the aisle between) took his bag as if he was about to go (though our bus stop is farther) but as I sat down he put his bag back. I have also the feeling he waits me to go down the bus at the same moment as me and since 1 day, he came in the hall like me (used to stay out) and when I went behind people (he couldn't see me anymore) he went to the other side but turned his back and the friend he was talking to kept glancing at me.
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+1 y
Also, in the bus, I was next to the window, his friend was already seated a few seats in front of me next to the window whe he came, so he sat in front of his friend and had to turn around to talk to him. I didn't look at him directly but I felt he saw I was there, glanced then turned back (like we should normally seat) and never looked behind again so his friend had to lean his way. But then again, though he didn't look at me, he suddenly stood up when I did and stood around my friends and I
Why would a guy avoid eye contact with the girl he is interested in?
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