I think the cringe is Yi Yun is showing his mom He Lingwei because he thinks his mom is her fan. However, his mom just wanted to support her niece. She can't explain that to him since he doesn't know so it's awkward. Other then that, I can't think of anything that could be cringy.
One of the few people on this site who's not underage
Feel free to give me any bl/yandere suggestions!
Fav BLs include: Whose Baby Is It, Bye Bye, Hold Me Tight, Psycho (Young Dream)