I like an introverted boy, who usually chats well by SMS (but I said it on my own initiative), but recently I found a girl watching him play basketball.

Can you tell whether he is really introverted or doesn't like talking to you? My ex-boyfriend himself is quite introverted, which I heard from others later, but after he met me, he was extremely enthusiastic. If his friend hadn't told me later, I didn't find the boy I was dating introverted at all, but after a long time, I found that he never talked to other girls except me, and only a few better buddies grew up together. So I think you should observe more. If that boy is introverted and loves to talk to you, it doesn't mean that to you. After all, no matter how introverted people are, opportunities will come to you. If he really likes you, he can't do nothing.