I could have sworn I’ve seen these two somewhere before… but now I can’t remember from where! I thought it was Bakemonogatari, but the character list doesn’t include a girl with flowers in her hair.
I hope someone recognizes them! Thanks to Michelle for sending this!
EDIT: Thanks to anon for letting me know this is Uiharu Kazari and Saten Ruiko from To Aru Kagaku no Railgun!