I must've forgotten something. Who the heck is the grey-haired girl in chapter 18?

Pink-haired girl actually. She's konatsu, a friend of kuro and uta. She first appeared in the last page of chapter 3 and fully appeared in chapter 8. She wasn't exactly introduced properly though, she just came out of nowhere so I also don't really know her about her character :/

Ah, thank you.