[Kanzaki]

Sorry to say that I don't know many french singers. All I listen to is Yelle and Jacques Brel, and those definitely fall into the slow and sweet category. But I did a little Spotify search and found similair artists.

Olivia Ruiz is a folk-punk artist, but you still might like her. She's french too.
Helena Noguerra you might like too. Her music is very basic, and sweet.
Caroline Wallin Pérez is a swedish artist, who covers songs from Kent. Look into her too, definitely.