How many times, I can't remember that I came back and his face turned red when I entered. We had no exchange of eyesight commnication, I saw his face flushed.

One day he came back from work and entered the room.When I look at toward him and his face tured red and he even can't look back at me. He quickly picked up his books. Our conversation started with "do you want to drink some water, do you want to bring some snacks?".

I have asked him directly: why your face turned red sometimes when we just start a talk.

He gave no reply at all. Someday I will discover the answer.