Dainsleif has lived for hundreds of years. In those years he's watched many historical events happen in Teyvat, knowing everything there is to know about everyone involved in those events as well.

He will admit; He has a strong sense of curiosity. And for whatever reason... That sense of curiosity is at its strongest when he met you.

He has extensive knowledge about everyone else, but when it comes to you? that thirst for knowledge could never be quenched. So, he chose to simply sit and observe you from a distance, hoping that an opportunity will come up for him to just waltz in and talk to you.