Kimi no sei
Kimi no sei is the opening song of the anime Seishun Buta Yarō. A weeb tends to sing with the opening, especially when it starts.
*opening starts*
Person 1: "Kimi no sei, Kimi no sei, Kimi no sei de watashi uwu"
Person 2: "Dude, whats wrong with you?"
Person 1: "Kimi no sei, Kimi no sei, Kimi no sei de watashi uwu"
Person 2: "Dude, whats wrong with you?"