Dengeki Daisy Vol 9

Dengeki Daisy Vol 9 by Kyousuke Motomi. A Shojo manga rated Older Teen, published in English by Viz Media in 2011.

After her brother's death, Teru's only lifeline is Daisy, an anonymous person who texts her support and secretly protects her. She starts to suspect Daisy might be Kurosaki, the rude, delinquent school janitor she's forced to work for. A charming romantic mystery.