to fall in love with someone whom you’re not supposed to have serious feelings for, such as idols, Youtubers/Vtubers, anime characters, employees at host/hostess clubs, or other sorts of “entertainers”
純愛, 両思い, 相思相愛
ガチ (serious) + 恋 (こい, love/romance). Not always, but it can have a negative connotation especially when it’s used to describe a man who seriously falls in love with a woman working in a hostess club, nightclub, or something similar. They are called ガチ恋客 (きゃく), “gachikoi customer”.
The person (or anime character) I stan is so handsome and I can’t help falling in love with him. So addictive.