Origin
A "secret seduction technique" that Frieren is said to have learned from her Master, shown in Chapter 28. It consists of her blowing a kiss in a more comedic than seductive way with o3o lips and a floating heart representing the kiss.
It had no effect on Sein, but had some effect on a young, inexperienced Stark and Fern, and has "mortally wounded" Himmel in the past.